ksh

NAME

ksh, rksh - KornShell, a standard/restricted command and
programming language

SYNOPSIS

/usr/bin/ksh [ + abCefhikmnoprstuvx ]
[ + o option ]
... [ arg ... ]

/usr/bin/ksh -c [ + abCefhikmnoprstuvx ]
[ + o option ]
... command_string [ command_name [ arg ... ] ]

/usr/xpg4/bin/sh [ + abCefhikmnoprstuvx ]
[ + o option ]
... [ arg ... ]

/usr/xpg4/bin/sh -c [ + abCefhikmnoprstuvx ]
[ + o option ]
... command_string [ command_name [ arg ... ] ]

/usr/bin/rksh [ + abCefhikmnoprstuvx ]
[ + o option ]
... [ arg ... ]

/usr/bin/rksh -c [ + abCefhikmnoprstuvx ]
[ + o option ]
... command_string [ command_name [ arg ... ] ]

DESCRIPTION

/usr/xpg4/bin/sh is identical to /usr/bin/ksh, a command and
programming language that executes commands read from a ter-
minal or a file. rksh is a restricted version of the command
interpreter ksh; it is used to set up login names and execu-
tion environments whose capabilities are more controlled
than those of the standard shell. See Invocation below for
the meaning of arguments to the shell.

Definitions
A metacharacter is one of the following characters:

; & ( ) | < > NEWLINE SPACE TAB

A blank is a TAB or a SPACE. An identifier is a sequence of
letters, digits, or underscores starting with a letter or
underscore. Identifiers are used as names for functions and
variables. A word is a sequence of characters separated by
one or more non-quoted metacharacters.

A command is a sequence of characters in the syntax of the
shell language. The shell reads each command and carries out
the desired action either directly or by invoking separate
utilities. A special-command is a command that is carried
out by the shell without creating a separate process.
Except for documented side effects, most special commands
can be implemented as separate utilities.

Commands
A simple-command is a sequence of blank-separated words
which may be preceded by a variable assignment list. (See
Environment below.) The first word specifies the name of the
command to be executed. Except as specified below, the
remaining words are passed as arguments to the invoked com-
mand. The command name is passed as argument 0 (see
exec(2)). The value of a simple-command is its exit status
if it terminates normally. If it terminates abnormally due
to receipt of a signal, the value is the signal number plus
128. See signal(3HEAD) for a list of signal values. Obvi-
ously, normal exit status values 129 to 255 cannot be dis-
tinguished from abnormal exit caused by receiving signal
numbers 1 to 127.

A pipeline is a sequence of one or more commands separated
by |. The standard output of each command but the last is
connected by a pipe(2) to the standard input of the next
command. Each command is run as a separate process; the
shell waits for the last command to terminate. The exit
status of a pipeline is the exit status of the last command.

A list is a sequence of one or more pipelines separated by
;, &, &&, or ||, and optionally terminated by ;, &, or |&.
Of these five symbols, ;, &, and |& have equal precedence,
which is lower than that of && and ||. The symbols && and ||
also have equal precedence. A semicolon (;) causes sequen-
tial execution of the preceding pipeline; an ampersand (&)
causes asynchronous execution of the preceding pipeline
(that is, the shell does not wait for that pipeline to fin-
ish). The symbol |& causes asynchronous execution of the
preceding command or pipeline with a two-way pipe esta-
blished to the parent shell.

The standard input and output of the spawned command can be
written to and read from by the parent shell using the -p
option of the special commands read and print described in
Special Commands. The symbol && (||) causes the list follow-
ing it to be executed only if the preceding pipeline returns
0 (or a non-zero) value. An arbitrary number of new-lines
may appear in a list, instead of a semicolon, to delimit a
command.

A command is either a simple-command or one of the follow-
ing. Unless otherwise stated, the value returned by a com-
mand is that of the last simple-command executed in the com-
mand.

for identifier [ in word ... ] ; do list ; done
Each time a for command is executed, identifier is
set to the next word taken from the in word list. If in
word ... is omitted, then the for command executes
the do list once for each positional parameter that is
set (see Parameter Substitution below). Execution
ends when there are no more words in the list.

select identifier [ in word ... ] ; do list ; done
A select command prints to standard error (file
descriptor 2), the set of words, each preceded by a
number. If in word ... is omitted, then the positional
parameters are used instead (see Parameter Substitu-
tion below). The PS3 prompt is printed and a line is
read from the standard input. If this line consists of
the number of one of the listed words, then the value
of the variable identifier is set to the word
corresponding to this number. If this line is empty
the selection list is printed again.
Otherwise the value of the variable identifier is set
to NULL. (See Blank Interpretation about NULL). The
contents of the line read from standard input is saved
in the shell variable REPLY. The list is executed for
each selection until a break or EOF is encountered. If
the REPLY variable is set to NULL by the execution of
list, then the selection list is printed before
displaying the PS3 prompt for the next selection.

case word in [ pattern [ | pattern ] ) list ;; ] ... esac
A case command executes the list associated with the
first pattern that matches word. The form of the pat-
terns is the same as that used for file-name genera-
tion (see File Name Generation below).

; ] fi
if list ; then list ; [ elif list ; then list ; ... ] [ else list
The list following if is executed and, if it returns
an exit status of 0, the list following the first then
is executed. Otherwise, the list following elif is
executed and, if its value is 0, the list following
the next then is executed. Failing that, the else
list is executed. If no else list or then list is exe-
cuted, then the if command returns 0 exit status.

while list ; do list ; done

until list ; do list ; done
A while command repeatedly executes the while list
and, if the exit status of the last command in the
list is 0, executes the do list; otherwise the loop
terminates. If no commands in the do list are exe-
cuted, then the while command returns 0 exit status;
until may be used in place of while to negate the loop
termination test.

(list)
Execute list in a separate environment. Note, that if
two adjacent open parentheses are needed for nesting,
a space must be inserted to avoid arithmetic evalua-
tion as described below.

{list}
list is simply executed. Note that unlike the meta-
characters ( and ), { and } are reserved words and
must occur at the beginning of a line or after a ; in
order to be recognized.

[[expression]]
Evaluates expression and returns 0 exit status when
expression is true. See Conditional Expressions
below, for a description of expression.

function identifier { list ;}

identifier() { list ;}
Define a function which is referenced by identifier.
The body of the function is the list of commands
between { and }. (See Functions below).

time pipeline
The pipeline is executed and the elapsed time as well
as the user and system time are printed to standard
error.

The following reserved words are only recognized as the
first word of a command and when not quoted:

! if then else elif fi case
esac for while until do done { }
function select time [[ ]]

Comments
A word beginning with # causes that word and all the follow-
ing characters up to a new-line to be ignored.

Aliasing
The first word of each command is replaced by the text of an
alias if an alias for this word has been defined. An alias
name consists of any number of characters excluding meta-
characters, quoting characters, file expansion characters,
parameter and command substitution characters, and =. The
replacement string can contain any valid shell script
including the metacharacters listed above. The first word
of each command in the replaced text, other than any that
are in the process of being replaced, will be tested for
aliases. If the last character of the alias value is a blank
then the word following the alias will also be checked for
alias substitution. Aliases can be used to redefine special
builtin commands but cannot be used to redefine the reserved
words listed above. Aliases can be created, listed, and
exported with the alias command and can be removed with the
unalias command. Exported aliases remain in effect for
scripts invoked by name, but must be reinitialized for
separate invocations of the shell (see Invocation below). To
prevent infinite loops in recursive aliasing, if the shell
is not currently processing an alias of the same name, the
word will be replaced by the value of the alias; otherwise,
it will not be replaced.

Aliasing is performed when scripts are read, not while they
are executed. Therefore, for an alias to take effect, the
alias definition command has to be executed before the com-
mand which references the alias is read.

Aliases are frequently used as a short hand for full path
names. An option to the aliasing facility allows the value
of the alias to be automatically set to the full pathname of
the corresponding command. These aliases are called tracked
aliases. The value of a tracked alias is defined the first
time the corresponding command is looked up and becomes
undefined each time the PATH variable is reset. These
aliases remain tracked so that the next subsequent reference
will redefine the value. Several tracked aliases are com-
piled into the shell. The -h option of the set command makes
each referenced command name into a tracked alias.

The following exported aliases are compiled into (and
built-in to) the shell but can be unset or redefined:

autoload='typeset -fu'
false='let 0'
functions='typeset -f'
hash='alias -t'
history='fc -l'
integer='typeset -i'
nohup='nohup '
r='fc -e -'
true=':'
type='whence -v'

An example concerning trailing blank characters and reserved
words follows. If the user types:

$ alias foo="/bin/ls "
$ alias while="/"

the effect of executing:

$ while true
> do
> echo "Hello, World"
> done

is a never-ending sequence of Hello, World strings to the
screen. However, if the user types:

$ foo while

the result will be an ls listing of /. Since the alias sub-
stitution for foo ends in a space character, the next word
is checked for alias substitution. The next word, while,
has also been aliased, so it is substituted as well. Since
it is not in the proper position as a command word, it is
not recognized as a reserved word.

If the user types:

$ foo; while

while retains its normal reserved-word properties.

Tilde Substitution
After alias substitution is performed, each word is checked
to see if it begins with an unquoted ~. If it does, then the
word up to a / is checked to see if it matches a user name.
If a match is found, the ~ and the matched login name are
replaced by the login directory of the matched user. This
is called a tilde substitution. If no match is found, the
original text is left unchanged. A ~ by itself, or in front
of a /, is replaced by $HOME. A ~ followed by a + or - is
replaced by $PWD and $OLDPWD respectively.

In addition, tilde substitution is attempted when the value
of a variable assignment begins with a ~.

Tilde Expansion
A tilde-prefix consists of an unquoted tilde character at
the beginning of a word, followed by all of the characters
preceding the first unquoted slash in the word, or all the
characters in the word if there is no slash. In an assign-
ment, multiple tilde-prefixes can be used: at the beginning
of the word (that is, following the equal sign of the
assignment), following any unquoted colon or both. A tilde-
prefix in an assignment is terminated by the first unquoted
colon or slash. If none of the characters in the tilde-
prefix are quoted, the characters in the tilde-prefix fol-
lowing the tilde are treated as a possible login name from
the user database.

A portable login name cannot contain characters outside the
set given in the description of the LOGNAME environment
variable. If the login name is null (that is, the tilde-
prefix contains only the tilde), the tilde-prefix will be
replaced by the value of the variable HOME. If HOME is
unset, the results are unspecified. Otherwise, the tilde-
prefix will be replaced by a pathname of the home directory
associated with the login name obtained using the getpwnam
function. If the system does not recognize the login name,
the results are undefined.

Tilde expansion generally occurs only at the beginning of
words, but an exception based on historical practice has
been included:

PATH=/posix/bin:~dgk/bin

is eligible for tilde expansion because tilde follows a
colon and none of the relevant characters is quoted. Con-
sideration was given to prohibiting this behavior because
any of the following are reasonable substitutes:

PATH=$ printf(%s ~karels/bin : ~bostic/bin)
for Dir in ~maart/bin ~srb/bin .
do
PATH=${PATH:+$PATH:}$Dir
done

With the first command, explicit colons are used for each
directory. In all cases, the shell performs tilde expansion
on each directory because all are separate words to the
shell.

Note that expressions in operands such as:

make -k mumble LIBDIR=~chet/lib

do not qualify as shell variable assignments and tilde
expansion is not performed (unless the command does so
itself, which make does not).

The special sequence $~ has been designated for future
implementations to evaluate as a means of forcing tilde
expansion in any word.

Because of the requirement that the word not be quoted, the
following are not equivalent; only the last will cause tilde
expansion:

\~hlj/ ~h\lj/ ~"hlj"/ ~hlj\/ ~hlj/

The results of giving tilde with an unknown login name are
undefined because the KornShell ~+ and ~- constructs make
use of this condition, but, in general it is an error to
give an incorrect login name with tilde. The results of hav-
ing HOME unset are unspecified because some historical
shells treat this as an error.

Command Substitution
The standard output from a command enclosed in parenthesis
preceded by a dollar sign (that is, $(command)) or a pair of
grave accents (``) may be used as part or all of a word;
trailing new-lines are removed. In the second (archaic)
form, the string between the quotes is processed for special
quoting characters before the command is executed. (See
Quoting below.) The command substitution $ cat(file) can be
replaced by the equivalent but faster $(<file). Command sub-
stitution of most special commands that do not perform
input/output redirection are carried out without creating a
separate process.

Command substitution allows the output of a command to be
substituted in place of the command name itself. Command
substitution occurs when the command is enclosed as follows:

$(command)

or (backquoted version):

`command`

The shell will expand the command substitution by executing
command in a subshell environment and replacing the command
substitution (the text of command plus the enclosing $() or
backquotes) with the standard output of the command,
removing sequences of one or more newline characters at the
end of the substitution. Embedded newline characters before
the end of the output will not be removed; however, they may
be treated as field delimiters and eliminated during field
splitting, depending on the value of IFS and quoting that is
in effect.

Within the backquoted style of command substitution,
backslash shall retain its literal meaning, except when fol-
lowed by:

$ ` \

(dollar-sign, backquote, backslash). The search for the
matching backquote is satisfied by the first backquote found
without a preceding backslash; during this search, if a
non-escaped backquote is encountered within a shell comment,
a here-document, an embedded command substitution of the
$(command) form, or a quoted string, undefined results
occur. A single- or double-quoted string that begins, but
does not end, within the `...` sequence produces undefined
results.

With the $(command) form, all characters following the open
parenthesis to the matching closing parenthesis constitute
the command. Any valid shell script can be used for command,
except:

+ A script consisting solely of redirections produces
unspecified results.

+ See the restriction on single subshells described
below.

The results of command substitution will not be field split-
ting and pathname expansion processed for further tilde
expansion, parameter expansion, command substitution or
arithmetic expansion. If a command substitution occurs
inside double-quotes, it will not be performed on the
results of the substitution.

Command substitution can be nested. To specify nesting
within the backquoted version, the application must precede
the inner backquotes with backslashes; for example:

`\`command\``

The $() form of command substitution solves a problem of
inconsistent behavior when using backquotes. For example:

Command | Output
echo '\$x' | \$x
echo `echo '\$x'` | $x
echo $(echo '\$x') | \$x

Additionally, the backquoted syntax has historical restric-
tions on the contents of the embedded command. While the new
$() form can process any kind of valid embedded script, the
backquoted form cannot handle some valid scripts that
include backquotes. For example, these otherwise valid
embedded scripts do not work in the left column, but do work
on the right:

Because of these inconsistent behaviors, the backquoted
variety of command substitution is not recommended for new
applications that nest command substitutions or attempt to
embed complex scripts.

If the command substitution consists of a single subshell,
such as:

$( (command) )

a portable application must separate the $( and ( into two
tokens (that is, separate them with white space). This is
required to avoid any ambiguities with arithmetic expansion.

Arithmetic Expansion
An arithmetic expression enclosed in double parentheses pre-
ceded by a dollar sign ( $((arithmetic-expression)) ) is
replaced by the value of the arithmetic expression within
the double parenthesis. Arithmetic expansion provides a
mechanism for evaluating an arithmetic expression and sub-
stituting its value. The format for arithmetic expansion is
as follows:

$((expression))

The expression is treated as if it were in double-quotes,
except that a double-quote inside the expression is not
treated specially. The shell will expand all tokens in the
expression for parameter expansion, command substitution and
quote removal.

Next, the shell will treat this as an arithmetic expression
and substitute the value of the expression. The arithmetic
expression will be processed according to the rules of the
ISO C with the following exceptions:

+ Only integer arithmetic is required.

+ The sizeof() operator and the prefix and postfix ++
and -- operators are not required.

+ Selection, iteration, and jump statements are not sup-
ported.

As an extension, the shell may recognize arithmetic expres-
sions beyond those listed. If the expression is invalid, the
expansion will fail and the shell will write a message to
standard error indicating the failure.

A simple example using arithmetic expansion:

# repeat a command 100 times
x=100
while [ $x -gt 0 ]
do
command
x=$(($x-1))
done

Process Substitution
This feature is available in SunOS and only on versions of
the UNIX operating system that support the /dev/fd directory
for naming open files. Each command argument of the form
<(list) or >(list) will run process list asynchronously con-
nected to some file in /dev/fd. The name of this file will
become the argument to the command. If the form with > is
selected, then writing on this file will provide input for
list. If < is used, then the file passed as an argument will
contain the output of the list process. For example,

paste <(cut -f1 file1) <(cut -f3 file2) | tee >(pro-
cess1) >(process2)

cuts fields 1 and 3 from the files file1 and file2, respec-
tively, pastes the results together, and sends it to the
processes process1 and process2, as well as putting it onto
the standard output. Note that the file, which is passed as
an argument to the command, is a UNIX pipe(2) so programs
that expect to lseek(2) on the file will not work.

Parameter Substitution
A parameter is an identifier, one or more digits, or any of
the characters *, @, #, ?, -, $, and !. A variable (a param-
eter denoted by an identifier) has a value and zero or more
attributes. variables can be assigned values and attributes
by using the typeset special command. The attributes sup-
ported by the shell are described later with the typeset
special command. Exported variables pass values and attri-
butes to the environment.

The shell supports a one-dimensional array facility. An ele-
ment of an array variable is referenced by a subscript. A
subscript is denoted by a [, followed by an arithmetic
expression (see Arithmetic Evaluation below) followed by a
]. To assign values to an array, use set -A name value ....
The value of all subscripts must be in the range of 0
through 4095. Arrays need not be declared. Any reference
to a variable with a valid subscript is legal and an array
will be created if necessary. Referencing an array without
a subscript is equivalent to referencing the element 0. If
an array identifier with subscript * or @ is used, then the
value for each of the elements is substituted (separated by
a field separator character).

The value of a variable may be assigned by writing:

name=value [ name=value ] ...

If the integer attribute, -i, is set for name, the value is
subject to arithmetic evaluation as described below.

Positional parameters, parameters denoted by a number, may
be assigned values with the set special command. Parameter
$0 is set from argument zero when the shell is invoked. If
parameter is one or more digits then it is a positional
parameter. A positional parameter of more than one digit
must be enclosed in braces.

Parameter Expansion
The format for parameter expansion is as follows:

${expression}

where expression consists of all characters until the match-
ing }. Any } escaped by a backslash or within a quoted
string, and characters in embedded arithmetic expansions,
command substitutions and variable expansions, are not exam-
ined in determining the matching }.

The simplest form for parameter expansion is:

${parameter}

The value, if any, of parameter will be substituted.

The parameter name or symbol can be enclosed in braces,
which are optional except for positional parameters with
more than one digit or when parameter is followed by a char-
acter that could be interpreted as part of the name. The
matching closing brace will be determined by counting brace
levels, skipping over enclosed quoted strings and command
substitutions.

If the parameter name or symbol is not enclosed in braces,
the expansion will use the longest valid name whether or not
the symbol represented by that name exists. When the shell
is scanning its input to determine the boundaries of a name,
it is not bound by its knowledge of what names are already
defined. For example, if F is a defined shell variable, the
command:

echo $Fred

does not echo the value of $F followed by red; it selects
the longest possible valid name, Fred, which in this case
might be unset.

If a parameter expansion occurs inside double-quotes:

+ Pathname expansion will not be performed on the
results of the expansion.

+ Field splitting will not be performed on the results
of the expansion, with the exception of @.

In addition, a parameter expansion can be modified by using
one of the following formats. In each case that a value of
word is needed (based on the state of parameter, as
described below), word will be subjected to tilde expansion,
parameter expansion, command substitution and arithmetic
expansion. If word is not needed, it will not be expanded.
The } character that delimits the following parameter expan-
sion modifications is determined as described previously in
this section and in dquote. (For example, ${foo-bar}xyz}
would result in the expansion of foo followed by the string
xyz} if foo is set, else the string barxyz}).

${parameter:-word}
Use Default Values. If parameter is unset or null,
the expansion of word will be substituted; otherwise,
the value of parameter will be substituted.

${parameter:=word}
Assign Default Values. If parameter is unset or null,
the expansion of word will be assigned to parameter.
In all cases, the final value of parameter will be
substituted. Only variables, not positional parame-
ters or special parameters, can be assigned in this
way.

${parameter:?[word]}
Indicate Error if Null or Unset. If parameter is unset
or null, the expansion of word (or a message indicat-
ing it is unset if word is omitted) will be written to
standard error and the shell will exit with a non-zero
exit status. Otherwise, the value of parameter will be
substituted. An interactive shell need not exit.

${parameter:+[word]}
Use Alternative Value. If parameter is unset or null,
null will be substituted; otherwise, the expansion of
word will be substituted.

In the parameter expansions shown previously, use of the
colon in the format results in a test for a parameter that
is unset or null; omission of the colon results in a test
for a parameter that is only unset. The following table sum-
marizes the effect of the colon:

parameter set and not null parameter set but null parameter unset
${parameter:-word} substitute parameter substitute word substitute word
${parameter-word} substitute parameter substitute null substitute word
${parameter:=word} substitute parameter assign word assign word
${parameter=word} substitute parameter substitute parameter assign null
${parameter:?word} substitute parameter error, exit error, exit
${parameter?word} substitute parameter substitute null error, exit
${parameter:+word} substitute word substitute null substitute null
${parameter+word} substitute word substitute word substitute null

In all cases shown with "substitute", the expression is
replaced with the value shown. In all cases shown with
"assign" parameter is assigned that value, which also
replaces the expression.

${#parameter}
String Length. The length in characters of the value
of parameter. If parameter is * or @, then all the
positional parameters, starting with $1, are substi-
tuted (separated by a field separator character).

The following four varieties of parameter expansion provide
for substring processing. In each case, pattern matching
notation (see patmat), rather than regular expression nota-
tion, will be used to evaluate the patterns. If parameter is
* or @, then all the positional parameters, starting with
$1, are substituted (separated by a field separator charac-
ter). Enclosing the full parameter expansion string in
double-quotes will not cause the following four varieties of
pattern characters to be quoted, whereas quoting characters
within the braces will have this effect.

${parameter%word}
Remove Smallest Suffix Pattern. The word will be
expanded to produce a pattern. The parameter expansion
then will result in parameter, with the smallest por-
tion of the suffix matched by the pattern deleted.

${parameter%%word}
Remove Largest Suffix Pattern. The word will be
expanded to produce a pattern. The parameter expansion
then will result in parameter, with the largest por-
tion of the suffix matched by the pattern deleted.

${parameter#word}
Remove Smallest Prefix Pattern. The word will be
expanded to produce a pattern. The parameter expansion
then will result in parameter, with the smallest por-
tion of the prefix matched by the pattern deleted.

${parameter##word}
Remove Largest Prefix Pattern. The word will be
expanded to produce a pattern. The parameter expansion
then will result in parameter, with the largest por-
tion of the prefix matched by the pattern deleted.

Examples:

${parameter:-word}

In this example, ls is executed only if x is null or
unset. (The $(ls) command substitution notation is
explained in Command Substitution above.)

${x:-$(ls)}

${parameter:=word}

unset X
echo ${X:=abc}
abc

${parameter:?word}

unset posix
echo ${posix:?}
sh: posix: parameter null or not set

${parameter:+word}

set a b c
echo ${3:+posix}
posix

${#parameter}

HOME=/usr/posix
echo ${#HOME}
10

${parameter%word}

x=file.c
echo ${x%.c}.o
file.o

${parameter%%word}

x=posix/src/std
echo ${x%%/*}
posix

${parameter#word}

x=$HOME/src/cmd
echo ${x#$HOME}
/src/cmd

${parameter##word}

x=/one/two/three
echo ${x##*/}
three

Parameters Set by Shell
The following parameters are automatically set by the shell:

# The number of positional parameters in decimal.

- Flags supplied to the shell on invocation or by the
set command.

? The decimal value returned by the last executed com-
mand.

$ The process number of this shell.

_ Initially, the value of _ is an absolute pathname of
the shell or script being executed as passed in the
environment. Subsequently it is assigned the last
argument of the previous command. This parameter is
not set for commands which are asynchronous. This
parameter is also used to hold the name of the match-
ing MAIL file when checking for mail.

! The process number of the last background command
invoked.

ERRNO The value of errno as set by the most recently failed
system call. This value is system dependent and is
intended for debugging purposes.

LINENO
The line number of the current line within the script
or function being executed.

OLDPWD
The previous working directory set by the cd command.

OPTARG
The value of the last option argument processed by the
getopts special command.

OPTIND
The index of the last option argument processed by the
getopts special command.

PPID The process number of the parent of the shell.

PWD The present working directory set by the cd command.

RANDOM
Each time this variable is referenced, a random
integer, uniformly distributed between 0 and 32767, is
generated. The sequence of random numbers can be ini-
tialized by assigning a numeric value to RANDOM.

REPLY This variable is set by the select statement and by
the read special command when no arguments are sup-
plied.

SECONDS
Each time this variable is referenced, the number of
seconds since shell invocation is returned. If this
variable is assigned a value, then the value returned
upon reference will be the value that was assigned
plus the number of seconds since the assignment.

Variables Used by Shell
The following variables are used by the shell:

CDPATH
The search path for the cd command.

COLUMNS
If this variable is set, the value is used to define
the width of the edit window for the shell edit modes
and for printing select lists.

EDITOR
If the value of this variable ends in emacs, gmacs, or
vi and the VISUAL variable is not set, then the
corresponding option (see the set special command
below) will be turned on.

ENV This variable, when the shell is invoked, is subjected
to parameter expansion by the shell and the resulting
value is used as a pathname of a file containing shell
commands to execute in the current environment. The
file need not be executable. If the expanded value of
ENV is not an absolute pathname, the results are
unspecified. ENV will be ignored if the user's real
and effective user IDs or real and effective group IDs
are different.

This variable can be used to set aliases and other
items local to the invocation of a shell. The file
referred to by ENV differs from $HOME/.profile in
that .profile is typically executed at session
startup, whereas the ENV file is executed at the
beginning of each shell invocation. The ENV value is
interpreted in a manner similar to a dot script, in
that the commands are executed in the current environ-
ment and the file needs to be readable, but not exe-
cutable. However, unlike dot scripts, no PATH search-
ing is performed. This is used as a guard against Tro-
jan Horse security breaches.

FCEDIT
The default editor name for the fc command.

FPATH The search path for function definitions. By default
the FPATH directories are searched after the PATH
variable. If an executable file is found, then it is
read and executed in the current environment. FPATH
is searched before PATH when a function with the -u
attribute is referenced. The preset alias autoload
causes a function with the -u attribute to be created.

IFS Internal field separators, normally space, tab, and
new-line that are used to separate command words which
result from command or parameter substitution and for
separating words with the special command read. The
first character of the IFS variable is used to
separate arguments for the $* substitution (See Quot-
ing below).

HISTFILE
If this variable is set when the shell is invoked,
then the value is the pathname of the file that will
be used to store the command history. (See Command
re-entry below.)

HISTSIZE
If this variable is set when the shell is invoked,
then the number of previously entered commands that
are accessible by this shell will be greater than or
equal to this number. The default is 128.

HOME The default argument (home directory) for the cd com-
mand.

LC_ALL
This variable provides a default value for the LC_*
variables.

LC_COLLATE
This variable determines the behavior of range expres-
sions, equivalence classes and multi-byte character
collating elements within pattern matching.

LC_CTYPE
Determines how the shell handles characters. When
LC_CTYPE is set to a valid value, the shell can
display and handle text and filenames containing valid
characters for that locale. If LC_CTYPE (see
environ(5)) is not set in the environment, the opera-
tional behavior of the shell is determined by the
value of the LANG environment variable. If LC_ALL is
set, its contents are used to override both the LANG
and the other LC_* variables.

LC_MESSAGES
This variable determines the language in which mes-
sages should be written.

LANG Provide a default value for the internationalization
variables that are unset or null. If any of the inter-
nationalization variables contains an invalid setting,
the utility will behave as if none of the variables
had been defined.

LINENO
This variable is set by the shell to a decimal number
representing the current sequential line number (num-
bered starting with 1) within a script or function
before it executes each command. If the user unsets or
resets LINENO, the variable may lose its special mean-
ing for the life of the shell. If the shell is not
currently executing a script or function, the value of
LINENO is unspecified.

LINES If this variable is set, the value is used to deter-
mine the column length for printing select lists.
Select lists will print vertically until about two-
thirds of LINES lines are filled.

MAIL If this variable is set to the name of a mail file and
the MAILPATH variable is not set, then the shell
informs the user of arrival of mail in the specified
file.

MAILCHECK
This variable specifies how often (in seconds) the
shell will check for changes in the modification time
of any of the files specified by the MAILPATH or
MAIL variables. The default value is 600 seconds.
When the time has elapsed the shell will check before
issuing the next prompt.

MAILPATH
A colon (:) separated list of file names. If this
variable is set, then the shell informs the user of
any modifications to the specified files that have
occurred within the last MAILCHECK seconds. Each file
name can be followed by a ? and a message that will be
printed. The message will undergo parameter substitu-
tion with the variable $_ defined as the name of the
file that has changed. The default message is you have
mail in $_.

NLSPATH
Determine the location of message catalogues for the
processing of LC_MESSAGES.

PATH The search path for commands (see Execution below).
The user may not change PATH if executing under rksh
(except in .profile).

PPID This variable is set by the shell to the decimal pro-
cess ID of the process that invoked the shell. In a
subshell, PPID will be set to the same value as that
of the parent of the current shell. For example, echo
$PPID and (echo $PPID) would produce the same value.

PS1 The value of this variable is expanded for parameter
substitution to define the primary prompt string which
by default is ``$ ''. The character ! in the primary
prompt string is replaced by the command number (see
Command Re-entry below). Two successive occurrences of
! will produce a single ! when the prompt string is
printed.

PS2 Secondary prompt string, by default ``> ''.

PS3 Selection prompt string used within a select loop, by
default ``#? ''.

PS4 The value of this variable is expanded for parameter
substitution and precedes each line of an execution
trace. If omitted, the execution trace prompt is ``+
''.

SHELL The pathname of the shell is kept in the environment.
At invocation, if the basename of this variable is
rsh, rksh, or krsh, then the shell becomes restricted.

TMOUT If set to a value greater than zero, the shell will
terminate if a command is not entered within the
prescribed number of seconds after issuing the PS1
prompt. (Note that the shell can be compiled with a
maximum bound for this value which cannot be
exceeded.)

VISUAL
If the value of this variable ends in emacs, gmacs, or
vi, then the corresponding option (see Special Command
set below) will be turned on.

The shell gives default values to PATH, PS1, PS2, PS3,
PS4, MAILCHECK, FCEDIT, TMOUT, and IFS, while HOME, SHELL,
ENV, and MAIL are not set at all by the shell (although HOME
is set by login(1)). On some systems MAIL and SHELL are also
set by login.

Blank Interpretation
After parameter and command substitution, the results of
substitutions are scanned for the field separator characters
(those found in IFS) and split into distinct arguments where
such characters are found. Explicit null arguments ( "" ) or
('') are retained. Implicit null arguments (those resulting
from parameters that have no values) are removed.

File Name Generation
Following substitution, each command word is scanned for the
characters *, ?, and [ unless the -f option has been set. If
one of these characters appears, the word is regarded as a
pattern. The word is replaced with lexicographically sorted
file names that match the pattern. If no file name is found
that matches the pattern, the word is left unchanged. When
a pattern is used for file name generation, the character
period (.) at the start of a file name or immediately fol-
lowing a /, as well as the character / itself, must be
matched explicitly. A file name beginning with a period will
not be matched with a pattern with the period inside
parentheses; that is,

ls .@(r*)

would locate a file named .restore, but ls @(.r*) would not.
In other instances of pattern matching the / and . are not
treated specially.

* Matches any string, including the null string.

? Matches any single character.

[...] Matches any one of the enclosed characters. A pair of
characters separated by - matches any character lexi-
cally between the pair, inclusive. If the first char-
acter following the opening "[ " is a "! ", then any
character not enclosed is matched. A - can be
included in the character set by putting it as the
first or last character.

A pattern-list is a list of one or more patterns separated
from each other with a |. Composite patterns can be formed
with one or more of the following:

?(pattern-list)
Optionally matches any one of the given patterns.

*(pattern-list)
Matches zero or more occurrences of the given
patterns.

+(pattern-list)
Matches one or more occurrences of the given patterns.

@(pattern-list)
Matches exactly one of the given patterns.

!(pattern-list)
Matches anything, except one of the given patterns.

Quoting
Each of the metacharacters listed above (See Definitions)
has a special meaning to the shell and causes termination of
a word unless quoted. A character may be quoted (that is,
made to stand for itself) by preceding it with a \. The pair
\NEWLINE is removed. All characters enclosed between a pair
of single quote marks ( ' ') are quoted. A single quote
cannot appear within single quotes. Inside double quote
marks (""), parameter and command substitution occur and \
quotes the characters \, `, ", and $. The meaning of $* and
$@ is identical when not quoted or when used as a parameter
assignment value or as a file name. However, when used as a
command argument, $* is equivalent to ``$1d$2d...'', where d
is the first character of the IFS variable, whereas $@ is
equivalent to $1 $2 .... Inside grave quote marks (``), \
quotes the characters \, ', and $. If the grave quotes occur
within double quotes, then \ also quotes the character ".

The special meaning of reserved words or aliases can be
removed by quoting any character of the reserved word. The
recognition of function names or special command names
listed below cannot be altered by quoting them.

Arithmetic Evaluation
An ability to perform integer arithmetic is provided with
the special command let. Evaluations are performed using
long arithmetic. Constants are of the form [ base# ] n where
base is a decimal number between two and thirty-six
representing the arithmetic base and n is a number in that
base. If base is omitted then base 10 is used.

An arithmetic expression uses the same syntax, precedence,
and associativity of expression as the C language. All the
integral operators, other than ++, -;, ?:, and , are sup-
ported. Variables can be referenced by name within an
arithmetic expression without using the parameter substitu-
tion syntax. When a variable is referenced, its value is
evaluated as an arithmetic expression.

An internal integer representation of a variable can be
specified with the -i option of the typeset special command.
Arithmetic evaluation is performed on the value of each
assignment to a variable with the -i attribute. If you do
not specify an arithmetic base, the first assignment to the
variable determines the arithmetic base. This base is used
when parameter substitution occurs.

Since many of the arithmetic operators require quoting, an
alternative form of the let command is provided. For any
command which begins with a ((, all the characters until a
matching )) are treated as a quoted expression. More pre-
cisely, ((...)) is equivalent to let "...".

Prompting
When used interactively, the shell prompts with the parame-
ter expanded value of PS1 before reading a command. If at
any time a new-line is typed and further input is needed to
complete a command, then the secondary prompt (that is, the
value of PS2) is issued.

Conditional Expressions
A conditional expression is used with the [[ compound com-
mand to test attributes of files and to compare strings.
Word splitting and file name generation are not performed on
the words between [[ and ]]. Each expression can be con-
structed from one or more of the following unary or binary
expressions:

-a file
True, if file exists.

-b file
True, if file exists and is a block special file.

-c file
True, if file exists and is a character special file.

-d file
True, if file exists and is a directory.

-e file
True, if file exists.

-f file
True, if file exists and is an ordinary file.

-g file
True, if file exists and is has its setgid bit set.

-k file
True, if file exists and is has its sticky bit set.

-n string
True, if length of string is non-zero.

-o option
True, if option named option is on.

-p file
True, if file exists and is a fifo special file or a
pipe.

-r file
True, if file exists and is readable by current pro-
cess.

-s file
True, if file exists and has size greater than zero.

-t fildes
True, if file descriptor number fildes is open and
associated with a terminal device.

-u file
True, if file exists and has its setuid bit set.

-w file
True, if file exists and is writable by current pro-
cess.

-x file
True, if file exists and is executable by current pro-
cess. If file exists and is a directory, then the
current process has permission to search in the direc-
tory.

-z string
True, if length of string is zero.

-L file
True, if file exists and is a symbolic link.

-O file
True, if file exists and is owned by the effective
user id of this process.

-G file
True, if file exists and its group matches the effec-
tive group id of this process.

-S file
True, if file exists and is a socket.

file1 -nt file2
True, if file1 exists and is newer than file2.

file1 -ot file2
True, if file1 exists and is older than file2.

file1 -ef file2
True, if file1 and file2 exist and refer to the same
file.

string
True if the string string is not the null string.

string = pattern
True, if string matches pattern.

string != pattern
True, if string does not match pattern.

string1=string2
True if the strings string1 and string2 are identical.

string1! =string2
True if the strings string1 and string2 are not ident-
ical.

string1 < string2
True, if string1 comes before string2 based on strings
interpreted as appropriate to the locale setting for
category LC_COLLATE.

string1 > string2
True, if string1 comes after string2 based on strings
interpreted as appropriate to the locale setting for
category LC_COLLATE.

exp1 -eq exp2
True, if exp1 is equal to exp2.

exp1 -ne exp2
True, if exp1 is not equal to exp2.

exp1 -lt exp2
True, if exp1 is less than exp2.

exp1 -gt exp2
True, if exp1 is greater than exp2.

exp1 -le exp2
True, if exp1 is less than or equal to exp2.

exp1 -ge exp2
True, if exp1 is greater than or equal to exp2.

In each of the above expressions, if file is of the form
/dev/fd/n, where n is an integer, then the test is applied
to the open file whose descriptor number is n.

A compound expression can be constructed from these primi-
tives by using any of the following, listed in decreasing
order of precedence.

(expression)
True, if expression is true. Used to group expres-
sions.

! expression
True if expression is false.

expression1 && expression2
True, if expression1 and expression2 are both true.

expression1 || expression2
True, if either expression1 or expression2 is true.

Input/Output
Before a command is executed, its input and output may be
redirected using a special notation interpreted by the
shell. The following may appear anywhere in a simple-command
or may precede or follow a command and are not passed on to
the invoked command. Command and parameter substitution
occur before word or digit is used except as noted below.
File name generation occurs only if the pattern matches a
single file, and blank interpretation is not performed.

<word Use file word as standard input file(descriptor 0).

>word Use file word as standard output file(descriptor 1).
If the file does not exist then it is created. If the
file exists, and the noclobber option is on, this
causes an error; otherwise, it is truncated to zero
length.

>|word
Sames as >, except that it overrides the noclobber
option.

>>word
Use file word as standard output. If the file exists
then output is appended to it (by first seeking to the
EOF); otherwise, the file is created.

<>word
Open file word for reading and writing as standard
input.

<< [-]word
The shell input is read up to a line that is the same
as word, or to an EOF. No parameter substitution,
command substitution or file name generation is per-
formed on word. The resulting document, called a
here-document, becomes the standard input. If any
character of word is quoted, then no interpretation is
placed upon the characters of the document; otherwise,
parameter and command substitution occur, \NEWLINE is
ignored, and \ must be used to quote the characters \,
$, `, and the first character of word. If - is
appended to <<, then all leading tabs are stripped
from word and from the document.

<&digit
The standard input is duplicated from file descriptor
digit (see dup(2)). Similarly for the standard output
using >&digit.

<&- The standard input is closed. Similarly for the stan-
dard output using >&-.

<&p The input from the co-process is moved to standard
input.

>&p The output to the co-process is moved to standard out-
put.

If one of the above is preceded by a digit, then the file
descriptor number referred to is that specified by the digit
(instead of the default 0 or 1). For example:

... 2>&1

means file descriptor 2 is to be opened for writing as a
duplicate of file descriptor 1.

The order in which redirections are specified is signifi-
cant. The shell evaluates each redirection in terms of the
file(descriptor, file) association at the time of evalua-
tion. For example:

... 1>fname 2>&1

first associates file descriptor 1 with file fname. It then
associates file descriptor 2 with the file associated with
file descriptor 1 (that is fname). If the order of redirec-
tions were reversed, file descriptor 2 would be associated
with the terminal (assuming file descriptor 1 had been) and
then file descriptor 1 would be associated with file fname.

If a command is followed by & and job control is not active,
then the default standard input for the command is the empty
file /dev/null. Otherwise, the environment for the execution
of a command contains the file descriptors of the invoking
shell as modified by input/output specifications.

Environment
The environment (see environ(5)) is a list of name-value
pairs that is passed to an executed program in the same way
as a normal argument list. The names must be identifiers
and the values are character strings.
The shell interacts with the environment in several ways.
On invocation, the shell scans the environment and creates a
variable for each name found, giving it the corresponding
value and marking it export. Executed commands inherit the
environment. If the user modifies the values of these vari-
ables or creates new ones, using the export or typeset -x
commands, they become part of the environment. The environ-
ment seen by any executed command is thus composed of any
name-value pairs originally inherited by the shell, whose
values may be modified by the current shell, plus any addi-
tions which must be noted in export or typeset -x commands.

The environment for any simple-command or function may be
augmented by prefixing it with one or more variable assign-
ments. A variable assignment argument is a word of the form
identifier=value. Thus:

TERM=450 cmd args

and

export(TERM; TERM=450; cmd args)

are equivalent (as far as the above execution of cmd is con-
cerned, except for special commands listed below that are
preceded with an asterisk).

If the -k flag is set, all variable assignment arguments are
placed in the environment, even if they occur after the com-
mand name. The following first prints a=b c and then c:

echo a=b c
set -k echo
a=b c

This feature is intended for use with scripts written for
early versions of the shell and its use in new scripts is
strongly discouraged. It is likely to disappear someday.

Functions
The function reserved word, described in the Commands sec-
tion above, is used to define shell functions. Shell func-
tions are read in and stored internally. Alias names are
resolved when the function is read. Functions are executed
like commands with the arguments passed as positional param-
eters. (See Execution below.)

Functions execute in the same process as the caller and
share all files and present working directory with the
caller. Traps caught by the caller are reset to their
default action inside the function.
A trap condition that is not caught or ignored by the func-
tion causes the function to terminate and the condition to
be passed on to the caller. A trap on EXIT set inside a
function is executed after the function completes in the
environment of the caller. Ordinarily, variables are shared
between the calling program and the function. However, the
typeset special command used within a function defines local
variables whose scope includes the current function and all
functions it calls.

The special command return is used to return from function
calls. Errors within functions return control to the
caller.

The names of all functions can be listed with typeset+f.
typeset -f lists all function names as well as the text of
all functions. typeset -f function-names lists the text of
the named functions only. Functions can be undefined with
the -f option of the unset special command.

Ordinarily, functions are unset when the shell executes a
shell script. The -xf option of the typeset command allows
a function to be exported to scripts that are executed
without a separate invocation of the shell. Functions that
need to be defined across separate invocations of the shell
should be specified in the ENV file with the -xf option of
typeset.

Function Definition Command
A function is a user-defined name that is used as a simple
command to call a compound command with new positional
parameters. A function is defined with a function definition
command.

The format of a function definition command is as follows:

fname() compound-command[io-redirect ...]

The function is named fname; it must be a name. An implemen-
tation may allow other characters in a function name as an
extension. The implementation will maintain separate name
spaces for functions and variables.

The () in the function definition command consists of two
operators. Therefore, intermixing blank characters with the
fname, (, and ) is allowed, but unnecessary.

The argument compound-command represents a compound command.

When the function is declared, none of the expansions in
wordexp will be performed on the text in compound-command or
io-redirect; all expansions will be performed as normal each
time the function is called. Similarly, the optional io-
redirect redirections and any variable assignments within
compound-command will be performed during the execution of
the function itself, not the function definition.

When a function is executed, it will have the syntax-error
and variable-assignment properties described for the special
built-in utilities.

The compound-command will be executed whenever the function
name is specified as the name of a simple command The
operands to the command temporarily will become the posi-
tional parameters during the execution of the compound-
command; the special parameter # will also be changed to
reflect the number of operands. The special parameter 0 will
be unchanged. When the function completes, the values of the
positional parameters and the special parameter # will be
restored to the values they had before the function was exe-
cuted. If the special built-in return is executed in the
compound-command, the function will complete and execution
will resume with the next command after the function call.

An example of how a function definition can be used wherever
a simple command is allowed:

# If variable i is equal to "yes",
# define function foo to be ls -l
#
[ "$i" = yes ] && foo() {
ls -l
}

The exit status of a function definition will be 0 if the
function was declared successfully; otherwise, it will be
greater than zero. The exit status of a function invocation
will be the exit status of the last command executed by the
function.

Jobs
If the monitor option of the set command is turned on, an
interactive shell associates a job with each pipeline. It
keeps a table of current jobs, printed by the jobs command,
and assigns them small integer numbers. When a job is
started asynchronously with &, the shell prints a line which
looks like:

[1] 1234

indicating that the job, which was started asynchronously,
was job number 1 and had one (top-level) process, whose pro-
cess id was 1234.

If you are running a job and wish to do something else you
may press the key ^Z (CTRL-Z) which sends a STOP signal to
the current job. The shell will then normally indicate that
the job has been `Stopped', and print another prompt. You
can then manipulate the state of this job, putting it in the
background with the bg command, or run some other commands
and then eventually bring the job back into the foreground
with the foreground command fg. A ^Z takes effect immedi-
ately and is like an interrupt in that pending output and
unread input are discarded when it is typed.

A job being run in the background will stop if it tries to
read from the terminal. Background jobs are normally allowed
to produce output, but this can be disabled by giving the
command "stty tostop". If you set this tty option, then
background jobs will stop when they try to produce output as
they do when they try to read input.

There are several ways to refer to jobs in the shell. A job
can be referred to by the process id of any process of the
job or by one of the following:

%number
The job with the given number.

%string
Any job whose command line begins with string.

%?string
Any job whose command line contains string.

%% Current job.

%+ Equivalent to %%.

%- Previous job.

The shell learns immediately whenever a process changes
state. It normally informs you whenever a job becomes
blocked so that no further progress is possible, but only
just before it prints a prompt. This is done so that it
does not otherwise disturb your work.

When the monitor mode is on, each background job that com-
pletes triggers any trap set for CHLD.

When you try to leave the shell while jobs are running or
stopped, you will be warned with the message `You have
stopped(running) jobs.' You may use the jobs command to see
what they are. If you do this or immediately try to exit
again, the shell will not warn you a second time, and the
stopped jobs will be terminated. If you have nohup'ed jobs
running when you attempt to logout, you will be warned with
the message:

You have jobs running.

You will then need to logout a second time to actually
logout; however, your background jobs will continue to run.

Signals
The INT and QUIT signals for an invoked command are ignored
if the command is followed by & and the monitor option is
not active. Otherwise, signals have the values inherited by
the shell from its parent (but see also the trap special
command below).

Execution
Each time a command is executed, the above substitutions are
carried out. If the command name matches one of the Special
Commands listed below, it is executed within the current
shell process. Next, the command name is checked to see if
it matches one of the user defined functions. If it does,
the positional parameters are saved and then reset to the
arguments of the function call. When the function completes
or issues a return, the positional parameter list is
restored and any trap set on EXIT within the function is
executed. The value of a function is the value of the last
command executed. A function is also executed in the current
shell process. If a command name is not a special command or
a user defined function, a process is created and an attempt
is made to execute the command via exec(2).

The shell variable PATH defines the search path for the
directory containing the command. Alternative directory
names are separated by a colon (:). The default path is
/bin:/usr/bin: (specifying /bin, /usr/bin, and the current
directory in that order). The current directory can be
specified by two or more adjacent colons, or by a colon at
the beginning or end of the path list. If the command name
contains a / then the search path is not used. Otherwise,
each directory in the path is searched for an executable
file. If the file has execute permission but is not a direc-
tory or an a.out file, it is assumed to be a file containing
shell commands. A sub-shell is spawned to read it. All
non-exported aliases, functions, and variables are removed
in this case. A parenthesized command is executed in a
sub-shell without removing non-exported quantities.

Command Re-entry
The text of the last HISTSIZE (default 128) commands entered
from a terminal device is saved in a history file. The file
$HOME/.sh_history
is used if the HISTFILE variable is not set or if the
file it names is not writable. A shell can access the com-
mands of all interactive shells which use the same named
HISTFILE. The special command fc is used to list or edit a
portion of this file. The portion of the file to be edited
or listed can be selected by number or by giving the first
character or characters of the command. A single command or
range of commands can be specified. If you do not specify an
editor program as an argument to fc then the value of the
variable FCEDIT is used. If FCEDIT is not defined, then
/bin/ed is used. The edited command(s) is printed and re-
executed upon leaving the editor. The editor name - is used
to skip the editing phase and to re-execute the command. In
this case a substitution parameter of the form old=new can
be used to modify the command before execution. For exam-
ple, if r is aliased to 'fc -e -' then typing 'r bad=good
c' will re-execute the most recent command which starts
with the letter c, replacing the first occurrence of the
string bad with the string good.

In-line Editing Option
Normally, each command line entered from a terminal device
is simply typed followed by a new-line (RETURN or LINEFEED).
If either the emacs, gmacs, or vi option is active, the user
can edit the command line. To be in either of these edit
modes set the corresponding option. An editing option is
automatically selected each time the VISUAL or EDITOR vari-
able is assigned a value ending in either of these option
names.

The editing features require that the user's terminal accept
RETURN as carriage return without line feed and that a space
must overwrite the current character on the screen.

The editing modes implement a concept where the user is
looking through a window at the current line. The window
width is the value of COLUMNS if it is defined, otherwise
80. If the window width is too small to display the prompt
and leave at least 8 columns to enter input, the prompt is
truncated from the left. If the line is longer than the win-
dow width minus two, a mark is displayed at the end of the
window to notify the user. As the cursor moves and reaches
the window boundaries the window will be centered about the
cursor. The mark is a > if the line extends on the right
side of the window, < if the line extends on the left, and *
if the line extends on both sides of the window.

The search commands in each edit mode provide access to the
history file. Only strings are matched, not patterns,
although a leading caret (^) in the string restricts the
match to begin at the first character in the line.

emacs Editing Mode
This mode is entered by enabling either the emacs or gmacs
option. The only difference between these two modes is the
way they handle ^T. To edit, move the cursor to the point
needing correction and then insert or delete characters or
words as needed. All the editing commands are control char-
acters or escape sequences. The notation for control charac-
ters is caret ( ^ ) followed by the character. For example,
^F is the notation for control F. This is entered by
depressing `f' while holding down the CTRL (control) key.
The SHIFT key is not depressed. (The notation ^? indicates
the DEL (delete) key.)

The notation for escape sequences is M- followed by a char-
acter. For example, M-f (pronounced Meta f) is entered by
depressing ESC (ascii 033) followed by `f'. (M-F would be
the notation for ESC followed by SHIFT (capital) `F'.)

All edit commands operate from any place on the line (not
just at the beginning). Neither the RETURN nor the LINEFEED
key is entered after edit commands except when noted.

^F Move cursor forward (right) one character.

M-f Move cursor forward one word. (The emacs editor's idea
of a word is a string of characters consisting of only
letters, digits and underscores.)

^B Move cursor backward (left) one character.

M-b Move cursor backward one word.

^A Move cursor to start of line.

^E Move cursor to end of line.

^]char
Move cursor forward to character char on current line.

M-^]char
Move cursor backward to character char on current
line.

^X^X Interchange the cursor and mark.

erase (User defined erase character as defined by the
stty(1) command, usually ^H or #.) Delete previous
character.

^D Delete current character.

M-d Delete current word.

M-^H (Meta-backspace) Delete previous word.

M-h Delete previous word.

M-^? (Meta-DEL) Delete previous word (if your interrupt
character is ^? (DEL, the default) then this command
will not work).

^T Transpose current character with next character in
emacs mode. Transpose two previous characters in gmacs
mode.

^C Capitalize current character.

M-c Capitalize current word.

M-l Change the current word to lower case.

^K Delete from the cursor to the end of the line. If
preceded by a numerical parameter whose value is less
than the current cursor position, then delete from
given position up to the cursor. If preceded by a
numerical parameter whose value is greater than the
current cursor position, then delete from cursor up to
given cursor position.

^W Kill from the cursor to the mark.

M-p Push the region from the cursor to the mark on the
stack.

kill (User defined kill character as defined by the stty(1)
command, usually ^G or @.) Kill the entire current
line. If two kill characters are entered in succes-
sion, all kill characters from then on cause a line
feed (useful when using paper terminals).

^Y Restore last item removed from line. (Yank item back
to the line.)

^L Line feed and print current line.

^@ (null character) Set mark.

M-space
(Meta space) Set mark.

J (New line) Execute the current line.

M (Return) Execute the current line.

eof End-of-file character, normally ^D, is processed as an
End-of-file only if the current line is null.

^P Fetch previous command. Each time ^P is entered the
previous command back in time is accessed. Moves back
one line when not on the first line of a multi-line
command.

M-< Fetch the least recent (oldest) history line.

M-> Fetch the most recent (youngest) history line.

^N Fetch next command line. Each time ^N is entered the
next command line forward in time is accessed.

^Rstring
Reverse search history for a previous command line
containing string. If a parameter of zero is given,
the search is forward. string is terminated by a
RETURN or NEW LINE. If string is preceded by a ^, the
matched line must begin with string. If string is
omitted, then the next command line containing the
most recent string is accessed. In this case a param-
eter of zero reverses the direction of the search.

^O Operate. Execute the current line and fetch the next
line relative to current line from the history file.

M-digits
(Escape) Define numeric parameter, the digits are
taken as a parameter to the next command. The com-
mands that accept a parameter are ^F, ^B, erase, ^C,
^D, ^K, ^R, ^P, ^N, ^], M-., M-^], M-_, M-b, M-c, M-d,
M-f, M-h, M-l and M-^H.

M-letter
Soft-key. Your alias list is searched for an alias by
the name _letter and if an alias of this name is
defined, its value will be inserted on the input
queue. The letter must not be one of the above meta-
functions.

M-[letter
Soft-key. Your alias list is searched for an alias by
the name __letter and if an alias of this name is
defined, its value will be inserted on the input
queue. The can be used to program functions keys on
many terminals.

M-. The last word of the previous command is inserted on
the line. If preceded by a numeric parameter, the
value of this parameter determines which word to
insert rather than the last word.

M-_ Same as M-..

M-* An asterisk is appended to the end of the word and a
file name expansion is attempted.

M-ESC File name completion. Replaces the current word with
the longest common prefix of all filenames matching
the current word with an asterisk appended. If the
match is unique, a / is appended if the file is a
directory and a space is appended if the file is not a
directory.

M-= List files matching current word pattern if an aster-
isk were appended.

^U Multiply parameter of next command by 4.

\ Escape next character. Editing characters, the user's
erase, kill and interrupt (normally ^?) characters may
be entered in a command line or in a search string if
preceded by a \. The \ removes the next character's
editing features (if any).

^V Display version of the shell.

M-# Insert a # at the beginning of the line and execute
it. This causes a comment to be inserted in the his-
tory file.

vi Editing Mode
There are two typing modes. Initially, when you enter a
command you are in the input mode. To edit, enter control
mode by typing ESC (033) and move the cursor to the point
needing correction and then insert or delete characters or
words as needed. Most control commands accept an optional
repeat count prior to the command.

When in vi mode on most systems, canonical processing is
initially enabled and the command will be echoed again if
the speed is 1200 baud or greater and it contains any con-
trol characters or less than one second has elapsed since
the prompt was printed. The ESC character terminates canoni-
cal processing for the remainder of the command and the user
can then modify the command line. This scheme has the
advantages of canonical processing with the type-ahead echo-
ing of raw mode.

If the option viraw is also set, the terminal will always
have canonical processing disabled. This mode is implicit
for systems that do not support two alternate end of line
delimiters, and may be helpful for certain terminals.

Input Edit Commands
By default the editor is in input mode.

erase (User defined erase character as defined by the
stty(1) command, usually ^H or #.) Delete previous
character.

^W Delete the previous blank separated word.

^D Terminate the shell.

^V Escape next character. Editing characters and the
user's erase or kill characters may be entered in a
command line or in a search string if preceded by a
^V. The ^V removes the next character's editing
features (if any).

\ Escape the next erase or kill character.

Motion Edit Commands
These commands will move the cursor.

[count]l
Cursor forward (right) one character.

[count]w
Cursor forward one alpha-numeric word.

[count]W
Cursor to the beginning of the next word that follows
a blank.

[count]e
Cursor to end of word.

[count]E
Cursor to end of the current blank delimited word.

[count]h
Cursor backward (left) one character.

[count]b
Cursor backward one word.

[count]B
Cursor to preceding blank separated word.

[count]|
Cursor to column count.

[count]fc
Find the next character c in the current line.

[count]Fc
Find the previous character c in the current line.

[count]tc
Equivalent to f followed by h.

[count]Tc
Equivalent to F followed by l.

[count];
Repeats count times, the last single character find
command, f, F, t, or T.

[count],
Reverses the last single character find command count
times.

0 Cursor to start of line.

^ Cursor to first non-blank character in line.

$ Cursor to end of line.

% Moves to balancing (, ), {, }, [, or ]. If cursor is
not on one of the above characters, the remainder of
the line is searched for the first occurrence of one
of the above characters first.

Search Edit Commands
These commands access your command history.

[count]k
Fetch previous command. Each time k is entered the
previous command back in time is accessed.

[count]-
Equivalent to k.

[count]j
Fetch next command. Each time j is entered, the next
command forward in time is accessed.

[count]+
Equivalent to j.

[count]G
The command number count is fetched. The default is
the least recent history command.

/string
Search backward through history for a previous command
containing string. string is terminated by a RETURN or
NEWLINE. If string is preceded by a ^, the matched
line must begin with string. If string is NULL, the
previous string will be used.

?string
Same as / except that search will be in the forward
direction.

n Search for next match of the last pattern to / or ?
commands.

N Search for next match of the last pattern to / or ?,
but in reverse direction. Search history for the
string entered by the previous / command.

Text Modification Edit Commands
These commands will modify the line.

a Enter input mode and enter text after the current
character.

A Append text to the end of the line. Equivalent to $a.

[count]cmotion

c[count]motion
Delete current character through the character that
motion would move the cursor to and enter input mode.
If motion is c, the entire line will be deleted and
input mode entered.

C Delete the current character through the end of line
and enter input mode. Equivalent to c$.

[count]s
Delete count characters and enter input mode.

S Equivalent to cc.

D Delete the current character through the end of line.
Equivalent to d$.

[count]dmotion

d[count]motion
Delete current character through the character that
motion would move to. If motion is d, the entire line
will be deleted.

i Enter input mode and insert text before the current
character.

I Insert text before the beginning of the line.
Equivalent to 0i.

[count]P
Place the previous text modification before the cur-
sor.

[count]p
Place the previous text modification after the cursor.

R Enter input mode and replace characters on the screen
with characters you type overlay fashion.

[count]rc
Replace the count character(s) starting at the current
cursor position with c, and advance the cursor.

[count]x
Delete current character.

[count]X
Delete preceding character.

[count].
Repeat the previous text modification command.

[count]~
Invert the case of the count character(s) starting at
the current cursor position and advance the cursor.

[count]_
Causes the count word of the previous command to be
appended and input mode entered. The last word is
used if count is omitted.

* Causes an * to be appended to the current word and
file name generation attempted. If no match is found,
it rings the bell.
Otherwise, the word is replaced by the matching pat-
tern and input mode is entered.

\ Filename completion. Replaces the current word with
the longest common prefix of all filenames matching
the current word with an asterisk appended. If the
match is unique, a / is appended if the file is a
directory and a space is appended if the file is not a
directory.

Other Edit Commands
Miscellaneous commands.

[count]ymotion

y[count]motion
Yank current character through character that motion
would move the cursor to and puts them into the delete
buffer. The text and cursor are unchanged.

Y Yanks from current position to end of line.
Equivalent to y$.

u Undo the last text modifying command.

U Undo all the text modifying commands performed on the
line.

[count]v
Returns the command fc -e ${VISUAL:-${EDITOR:-vi}}
count in the input buffer. If count is omitted, then
the current line is used.

^L Line feed and print current line. Has effect only in
control mode.

J (New line) Execute the current line, regardless of
mode.

M (Return) Execute the current line, regardless of mode.

# If the first character of the command is a #, then
this command deletes this # and each # that follows a
newline. Otherwise, sends the line after inserting a
# in front of each line in the command. Useful for
causing the current line to be inserted in the history
as a comment and removing comments from previous com-
ment commands in the history file.

= List the file names that match the current word if an
asterisk were appended it.

@letter
Your alias list is searched for an alias by the name
_letter and if an alias of this name is defined, its
value will be inserted on the input queue for process-
ing.

Special Commands
The following simple-commands are executed in the shell pro-
cess. Input/Output redirection is permitted. Unless other-
wise indicated, the output is written on file descriptor 1
and the exit status, when there is no syntax error, is 0.
Commands that are preceded by one or two * (asterisks) are
treated specially in the following ways:

1. Variable assignment lists preceding the command remain in
effect when the command completes.

2. I/O redirections are processed after variable assign-
ments.

3. Errors cause a script that contains them to abort.

4. Words, following a command preceded by ** that are in the
format of a variable assignment, are expanded with the
same rules as a variable assignment. This means that
tilde substitution is performed after the = sign and word
splitting and file name generation are not performed.

* : [ arg ... ]
The command only expands parameters.

* . file [ arg ... ]
Read the complete file then execute the commands. The
commands are executed in the current shell environ-
ment. The search path specified by PATH is used to
find the directory containing file. If any arguments
arg are given, they become the positional parameters.
Otherwise the positional parameters are unchanged. The
exit status is the exit status of the last command
executed.

** alias [ -tx ] [ name[ =value ] ] ...
alias with no arguments prints the list of aliases in
the form name=value on standard output. An alias is
defined for each name whose value is given. A trail-
ing space in value causes the next word to be checked
for alias substitution. The -t flag is used to set
and list tracked aliases. The value of a tracked alias
is the full pathname corresponding to the given name.
The value becomes undefined when the value of PATH is
reset but the aliases remained tracked. Without the
-t flag, for each name in the argument list for which
no value is given, the name and value of the alias is
printed. The -x flag is used to set or print exported
aliases. An exported alias is defined for scripts
invoked by name. The exit status is non-zero if a
name is given, but no value, and no alias has been
defined for the name.

bg [ %job... ]
This command is only on systems that support job con-
trol. Puts each specified job into the background.
The current job is put in the background if job is not
specified. See "Jobs" section above for a description
of the format of job.

* break [ n ]
Exit from the enclosed for, while, until, or select
loop, if any. If n is specified then break n levels.

* continue [ n ]
Resume the next iteration of the enclosed for, while,
until, or select loop. If n is specified then resume
at the n-th enclosed loop.

cd [ arg ]

cd old new
This command can be in either of two forms. In the
first form it changes the current directory to arg. If
arg is - the directory is changed to the previous
directory. The shell variable HOME is the default
arg. The variable PWD is set to the current directory.
The shell variable CDPATH defines the search
path for the directory containing arg. Alternative
directory names are separated by a colon (:). The
default path is null (specifying the current direc-
tory). Note that the current directory is specified by
a null path name, which can appear immediately after
the equal sign or between the colon delimiters any-
where else in the path list. If arg begins with a /
then the search path is not used. Otherwise, each
directory in the path is searched for arg.

The second form of cd substitutes the string new for
the string old in the current directory name, PWD and
tries to change to this new directory. The cd command
may not be executed by rksh.

command [-p] [command_name] [argument ...]

command [-v -V] command_name
The command utility causes the shell to treat the
arguments as a simple command, suppressing the shell
function lookup. The -p flag performs the command
search using a default value for PATH that is
guaranteed to find all of the standard utilities. The
-v flag writes a string to standard output that indi-
cates the pathname or command that will be used by the
shell, in the current shell execution environment, to
invoke command_name. The -V flag writes a string to
standard output that indicates how the name given in
the command_name operand will be interpreted by the
shell, in the current shell execution environment.

echo [ arg ... ]
See echo(1) for usage and description.

* eval [ arg ... ]
The arguments are read as input to the shell and the
resulting command(s) executed.

* exec [ arg ... ]
If arg is given, the command specified by the argu-
ments is executed in place of this shell without
creating a new process. Input/output arguments may
appear and affect the current process. If no arguments
are given the effect of this command is to modify file
descriptors as prescribed by the input/output redirec-
tion list. In this case, any file descriptor numbers
greater than 2 that are opened with this mechanism are
closed when invoking another program.

* exit [ n ]
Causes the calling shell or shell script to exit with
the exit status specified by n. The value will be the
least significant 8 bits of the specified status. If n
is omitted then the exit status is that of the last
command executed. When exit occurs when executing a
trap, the last command refers to the command that exe-
cuted before the trap was invoked. An EOF will also
cause the shell to exit except for a shell which has
the ignoreeof option (See set below) turned on.

** export [ name[=value] ] ...
The given names are marked for automatic export to the
environment of subsequently-executed commands.

fc [ -e ename ] [ -nlr ] [ first [ last ] ]

fc -e - [ old=new ] [ command ]
In the first form, a range of commands from first to
last is selected from the last HISTSIZE commands that
were typed at the terminal. The arguments first and
last may be specified as a number or as a string. A
string is used to locate the most recent command
starting with the given string. A negative number is
used as an offset to the current command number. If
the -l flag is selected, the commands are listed on
standard output. Otherwise, the editor program ename
is invoked on a file containing these keyboard com-
mands. If ename is not supplied, then the value of
the variable FCEDIT (default /bin/ed) is used as the
editor. When editing is complete, the edited
command(s) is executed. If last is not specified then
it will be set to first. If first is not specified the
default is the previous command for editing and -16
for listing. The flag -r reverses the order of the
commands and the flag -n suppresses command numbers
when listing. In the second form the command is re-
executed after the substitution old=new is performed.
If there is not a command argument, the most recent
command typed at this terminal is executed.

fg [ %job... ]
This command is only on systems that support job con-
trol. Each job specified is brought to the fore-
ground. Otherwise, the current job is brought into
the foreground. See "Jobs" section above for a
description of the format of job.

getopts optstring name [ arg ... ]
Checks arg for legal options. If arg is omitted, the
positional parameters are used. An option argument
begins with a + or a -. An option not beginning with +
or - or the argument - ends the options. optstring
contains the letters that getopts recognizes. If a
letter is followed by a :, that option is expected to
have an argument. The options can be separated from
the argument by blanks.

getopts places the next option letter it finds inside
variable name each time it is invoked with a +
prepended when arg begins with a +. The index of the
next arg is stored in OPTIND. The option argument, if
any, gets stored in OPTARG.

A leading : in optstring causes getopts to store the
letter of an invalid option in OPTARG, and to set name
to ? for an unknown option and to : when a required
option is missing. Otherwise, getopts prints an error
message. The exit status is non-zero when there are
no more options. See getoptcvt(1) for usage and
description.

hash [ name ... ]
For each name, the location in the search path of the
command specified by name is determined and remembered
by the shell. The -r option causes the shell to forget
all remembered locations. If no arguments are given,
information about remembered commands is presented.
Hits is the number of times a command has been invoked
by the shell process. Cost is a measure of the work
required to locate a command in the search path. If a
command is found in a "relative" directory in the
search path, after changing to that directory, the
stored location of that command is recalculated. Com-
mands for which this will be done are indicated by an
asterisk (*) adjacent to the hits information. Cost
will be incremented when the recalculation is done.

jobs [ -lnp ] [ %job ... ]
Lists information about each given job; or all active
jobs if job is omitted. The -l flag lists process ids
in addition to the normal information. The -n flag
displays only jobs that have stopped or exited since
last notified. The -p flag causes only the process
group to be listed. See "Jobs" section above and
jobs(1) for a description of the format of job.

kill [ -sig ] %job ...

kill [ -sig ] pid ...

kill -l
Sends either the TERM (terminate) signal or the speci-
fied signal to the specified jobs or processes. Sig-
nals are either given by number or by names (as given
in signal(3HEAD) stripped of the prefix ``SIG'' with
the exception that SIGCHD is named CHLD). If the sig-
nal being sent is TERM (terminate) or HUP (hangup),
then the job or process will be sent a CONT (continue)
signal if it is stopped. The argument job can be the
process id of a process that is not a member of one of
the active jobs. See Jobs for a description of the
format of job. In the second form, kill -l, the signal
numbers and names are listed.

let arg...
Each arg is a separate arithmetic expression to be
evaluated. See the Arithmetic Evaluation section
above, for a description of arithmetic expression
evaluation.

The exit status is 0 if the value of the last expres-
sion is non-zero, and 1 otherwise.

* newgrp [ arg ... ]
Equivalent to exec /bin/newgrp arg ....

print [ -Rnprsu[n ] ] [ arg ... ]
The shell output mechanism.
With no flags or with flag - or -, the arguments are
printed on standard output as described by echo(1).
The exit status is 0, unless the output file is not
open for writing.

-n Suppress NEWLINE from being added to the output.

-R | -r
Raw mode. Ignore the escape conventions of
echo. The -R option will print all subsequent
arguments and options other than -n.

-p Write the arguments to the pipe of the process
spawned with |& instead of standard output.

-s Write the arguments to the history file instead
of standard output.

-u [ n ]
Specify a one digit file descriptor unit number
n on which the output will be placed.
The default is 1.

pwd Equivalent to print -r - $PWD.

read [ -prsu[ n ] ] [ name?prompt ] [ name ... ]
The shell input mechanism. One line is read and is
broken up into fields using the characters in IFS as
separators. The escape character, (\), is used to
remove any special meaning for the next character and
for line continuation. In raw mode, -r, the \ charac-
ter is not treated specially. The first field is
assigned to the first name, the second field to the
second name, etc., with leftover fields assigned to
the last name. The -p option causes the input line to
be taken from the input pipe of a process spawned by
the shell using |&. If the -s flag is present, the
input will be saved as a command in the history file.
The flag -u can be used to specify a one digit file
descriptor unit n to read from. The file descriptor
can be opened with the exec special command. The
default value of n is 0. If name is omitted then REPLY
is used as the default name. The exit status is 0
unless the input file is not open for reading or an
EOF is encountered. An EOF with the -p option causes
cleanup for this process so that another can be
spawned. If the first argument contains a ?, the
remainder of this word is used as a prompt on standard
error when the shell is interactive. The exit status
is 0 unless an EOF is encountered.

** readonly [ name[=value] ] ...
The given names are marked readonly and these names
cannot be changed by subsequent assignment.

* return [ n ]
Causes a shell function or '.' script to return to the
invoking script with the return status specified by n.
The value will be the least significant 8 bits of the
specified status. If n is omitted then the return
status is that of the last command executed. If
return is invoked while not in a function or a '.'
script, then it is the same as an exit.

]
set [ +abCefhkmnopstuvx ] [ +o option ]... [ +A name ] [ arg ...
The flags for this command have meaning as follows:

-A Array assignment. Unset the variable name and
assign values sequentially from the list arg. If
+A is used, the variable name is not unset
first.

-a All subsequent variables that are defined are
automatically exported.

-b Causes the shell to notify the user asynchro-
nously of background job completions. The fol-
lowing message will be written to standard
error:

"[%d]%c %s%s\n", <job-number>, <current>,
<status>, <job-name>

where the fields are as follows:
<current>
The character + identifies the job that
would be used as a default for the fg or
bg utilities; this job can also be speci-
fied using the job_id %+ or %%. The char-
acter - identifies the job that would
become the default if the current default
job were to exit; this job can also be
specified using the job_id %-. For other
jobs, this field is a space character. At
most one job can be identified with + and
at most one job can be identified with -.
If there is any suspended job, then the
current job will be a suspended job. If
there are at least two suspended jobs,
then the previous job will also be a
suspended job.

<job-number>
A number that can be used to identify the
process group to the wait, fg, bg, and
kill utilities. Using these utilities, the
job can be identified by prefixing the job
number with %.

<status>
Unspecified.

<job-name>
Unspecified.

When the shell notifies the user a job has been
completed, it may remove the job's process ID
from the list of those known in the current
shell execution environment. Asynchronous notif-
ication will not be enabled by default.

-C Prevent existing files from being overwritten by
the shell's > redirection operator; the >|
redirection operator will override this
noclobber option for an individual file.

-e If a command has a non-zero exit status, execute
the ERR trap, if set, and exit. This mode is
disabled while reading profiles.

-f Disables file name generation.

-h Each command becomes a tracked alias when first
encountered.

-k All variable assignment arguments are placed in
the environment for a command, not just those
that precede the command name.

-m Background jobs will run in a separate process
group and a line will print upon completion.
The exit status of background jobs is reported
in a completion message. On systems with job
control, this flag is turned on automatically
for interactive shells.

-n Read commands and check them for syntax errors,
but do not execute them. Ignored for interac-
tive shells.

-o The following argument can be one of the follow-
ing option names:

allexport
Same as -a.

errexit
Same as -e.

bgnice
All background jobs are run at a lower
priority. This is the default mode.

emacs Puts you in an emacs style in-line editor
for command entry.

gmacs Puts you in a gmacs style in-line editor
for command entry.

ignoreeof
The shell will not exit onEOF. The com-
mand exit must be used.

keyword
Same as -k.

markdirs
All directory names resulting from file
name generation have a trailing /
appended.

monitor
Same as -m.

noclobber
Prevents redirection > from truncating
existing files. Require >| to truncate a
file when turned on. Equivalent to -C.

noexec
Same as -n.

noglob
Same as -f.

nolog Do not save function definitions in his-
tory file.

notify
Equivalent to -b.

nounset
Same as -u.

privileged
Same as -p.

verbose
Same as -v.

trackall
Same as -h.

vi Puts you in insert mode of a vi style in-
line editor until you hit escape character
033. This puts you in control mode. A
return sends the line.

viraw Each character is processed as it is typed
in vi mode.

xtrace
Same as -x.

If no option name is supplied, the current
option settings are printed.

-p Disables processing of the $HOME/.profile
file and uses the file /etc/suid_profile instead
of the ENV file. This mode is on whenever the
effective uid is not equal to the real uid, or
when the effective gid is not equal to the real
gid. Turning this off causes the effective uid
and gid to be set to the real uid and gid.

-s Sort the positional parameters lexicographi-
cally.

-t Exit after reading and executing one command.
-u Treat unset parameters as an error when substi-
tuting.

-v Print shell input lines as they are read.

-x Print commands and their arguments as they are
executed.

- Turns off -x and -v flags and stops examining
arguments for flags.

-- Do not change any of the flags; useful in set-
ting $1 to a value beginning with -. If no
arguments follow this flag then the positional
parameters are unset.

Using + rather than - causes these flags to be
turned off. These flags can also be used upon
invocation of the shell. The current set of
flags may be found in $-. Unless -A is speci-
fied, the remaining arguments are positional
parameters and are assigned, in order, to $1 $2
.... If no arguments are given, the names and
values of all variables are printed on the stan-
dard output.

* shift [ n ]
The positional parameters from $n+1 $n+1 ... are
renamed $1 ..., default n is 1. The parameter n can be
any arithmetic expression that evaluates to a non-
negative number less than or equal to $#.

stop%jobid ...

stop pid ...
stop stops the execution of a background job(s) by
using its jobid, or of any process by using its pid.
(see ps(1)).

suspend
Stops the execution of the current shell (but not if
it is the login shell).

test expression
Evaluate conditional expressions. See Conditional
Expressions section above and test(1) for usage and
description.

* times
Print the accumulated user and system times for the
shell and for processes run from the shell.

* trap [ arg sig ... ]
arg is a command to be read and executed when the
shell receives signal(s) sig. arg is scanned once when
the trap is set and once when the trap is taken. sig
can be specified as a signal number or signal name.
trap commands are executed in order of signal number.
Any attempt to set a trap on a signal number that was
ignored on entry to the current shell is ineffective.

If arg is -, the shell will reset each sig to the
default value. If arg is null (''), the shell will
ignore each specified sig if it arises. Otherwise, arg
will be read and executed by the shell when one of the
corresponding sigs arises. The action of the trap
will override a previous action (either default action
or one explicitly set). The value of $? after the trap
action completes will be the value it had before the
trap was invoked.

sig can be EXIT, 0 (equivalent to EXIT) or a signal
specified using a symbolic name, without the SIG pre-
fix, for example, HUP, INT, QUIT, TERM. If sig is 0 or
EXIT and the trap statement is executed inside the
body of a function, then the command arg is executed
after the function completes. If sig is 0 or EXIT for
a trap set outside any function, the command arg is
executed on exit from the shell. If sig is ERR, arg
will be executed whenever a command has a non-zero
exit status. If sig is DEBUG, arg will be executed
after each command.

The environment in which the shell executes a trap on
EXIT will be identical to the environment immediately
after the last command executed before the trap on
EXIT was taken.

Each time the trap is invoked, arg will be processed
in a manner equivalent to:

eval "$arg"

Signals that were ignored on entry to a non-interactive
shell cannot be trapped or reset, although no error need be
reported when attempting to do so. An interactive shell may
reset or catch signals ignored on entry. Traps will remain
in place for a given shell until explicitly changed with
another trap command.

When a subshell is entered, traps are set to the default
args. This does not imply that the trap command cannot be
used within the subshell to set new traps.

The trap command with no arguments will write to standard
output a list of commands associated with each sig. The for-
mat is:

trap -- %s %s ... <arg>, <sig> ...

The shell will format the output, including the proper use
of quoting, so that it is suitable for reinput to the shell
as commands that achieve the same trapping results. For
example:

save_traps=$(trap)
...
eval "$save_traps"

If the trap name or number is invalid, a non-zero exit
status will be returned; otherwise, 0 will be returned. For
both interactive and non-interactive shells, invalid signal
names or numbers will not be considered a syntax error and
will not cause the shell to abort.

Traps are not processed while a job is waiting for a
foreground process. Thus, a trap on CHLD won't be
executed until the foreground job terminates.

type name ...
For each name, indicate how it would be interpreted if
used as a command name.

** typeset [ +HLRZfilrtux[n] ] [ name[=value
] ] ..." 6 Sets attributes and values for shell vari-
ables and functions. When typeset is invoked inside a
function, a new instance of the variables name is
created. The variables value and type are restored
when the function completes. The following list of
attributes may be specified:

-H This flag provides UNIX to host-name file map-
ping on non-UNIX machines.

-L Left justify and remove leading blanks from
value. If n is non-zero it defines the width of
the field; otherwise, it is determined by the
width of the value of first assignment. When the
variable is assigned to, it is filled on the
right with blanks or truncated, if necessary, to
fit into the field. Leading zeros are removed if
the -Z flag is also set. The -R flag is turned
off.

-R Right justify and fill with leading blanks. If
n is non-zero it defines the width of the field,
otherwise it is determined by the width of the
value of first assignment. The field is left
filled with blanks or truncated from the end if
the variable is reassigned. The -L flag is
turned off.

-Z Right justify and fill with leading zeros if the
first non-blank character is a digit and the -L
flag has not been set. If n is non-zero it
defines the width of the field; otherwise, it is
determined by the width of the value of first
assignment.

-f The names refer to function names rather than
variable names. No assignments can be made and
the only other valid flags are -t, -u, and -x.
The flag -t turns on execution tracing for this
function. The flag -u causes this function to
be marked undefined. The FPATH variable will be
searched to find the function definition when
the function is referenced. The flag -x allows
the function definition to remain in effect
across shell procedures invoked by name.

-i Parameter is an integer. This makes arithmetic
faster. If n is non-zero it defines the output
arithmetic base; otherwise, the first assignment
determines the output base.

-l All upper-case characters are converted to
lower-case. The upper-case flag, -u is turned
off.

-r The given names are marked readonly and these
names cannot be changed by subsequent assign-
ment.

-t Tags the variables. Tags are user definable and
have no special meaning to the shell.

-u All lower-case characters are converted to
upper-case characters. The lower-case flag, -l
is turned off.

-x The given names are marked for automatic export
to the environment of subsequently-executed
commands.

The -i attribute can not be specified along with -R, -L, -Z,
or -f.

Using + rather than - causes these flags to be turned
off. If no name arguments are given but flags are
specified, a list of names (and optionally the values)
of the variables which have these flags set is
printed. (Using + rather than - keeps the values from
being printed.) If no names and flags are given, the
names and attributes of all variables are printed.

ulimit [ -HSacdfnstv ] [ limit ]
Set or display a resource limit. The available
resources limits are listed below. Many systems do
not contain one or more of these limits. The limit
for a specified resource is set when limit is speci-
fied. The value of limit can be a number in the unit
specified below with each resource, or the value
unlimited. The H and S flags specify whether the hard
limit or the soft limit for the given resource is set.
A hard limit cannot be increased once it is set. A
soft limit can be increased up to the value of the
hard limit. If neither the H or S options is speci-
fied, the limit applies to both. The current resource
limit is printed when limit is omitted.
In this case the soft limit is printed unless H is
specified. When more that one resource is specified,
then the limit name and unit is printed before the
value.

-a Lists all of the current resource limits.

-c The number of 512-byte blocks on the size of
core dumps.

-d The number of K-bytes on the size of the data
area.

-f The number of 512-byte blocks on files written
by child processes (files of any size may be
read).

-n The number of file descriptors plus 1.

-s The number of K-bytes on the size of the stack
area.

-t The number of seconds to be used by each pro-
cess.

-v The number of K-bytes for virtual memory.

If no option is given, -f is assumed.

umask [-S] [ mask ]
The user file-creation mask is set to mask (see
umask(2)). mask can either be an octal number or a
symbolic value as described in chmod(1). If a symbolic
value is given, the new umask value is the complement
of the result of applying mask to the complement of
the previous umask value. If mask is omitted, the
current value of the mask is printed. The -S flag pro-
duces symbolic output.

unalias name...
The aliases given by the list of names are removed
from the alias list.

unset [ -f ] name ...
The variables given by the list of names are unas-
signed, that is, their values and attributes are
erased. readonly variables cannot be unset. If the
-f, flag is set, then the names refer to function
names. Unsetting ERRNO, LINENO, MAILCHECK, OPTARG,
OPTIND, RANDOM, SECONDS, TMOUT, and _ removes their
special meaning even if they are subsequently assigned
to.

* wait [ job ]
Wait for the specified job and report its termination
status. If job is not given then all currently active
child processes are waited for. The exit status from
this command is that of the process waited for. See
Jobs for a description of the format of job.

whence [ -pv ] name ...
For each name, indicate how it would be interpreted if
used as a command name.

The -v flag produces a more verbose report.

The -p flag does a path search for name even if name
is an alias, a function, or a reserved word.

Invocation
If the shell is invoked by exec(2), and the first character
of argument zero ($0) is -, then the shell is assumed to be
a login shell and commands are read from /etc/profile and
then from either .profile in the current directory or
$HOME/.profile, if either file exists. Next, commands are
read from the file named by performing parameter substitu-
tion on the value of the environment variable ENV if the
file exists. If the -s flag is not present and arg is, then
a path search is performed on the first arg to determine the
name of the script to execute. The script arg must have read
permission and any setuid and setgid settings will be
ignored. If the script is not found on the path, arg is
processed as if it named a builtin command or function. Com-
mands are then read as described below; the following flags
are interpreted by the shell when it is invoked:

-c Read commands from the command_string operand. Set
the value of special parameter 0 from the value of the
command_name operand and the positional parameters
($1, $2, and so on) in sequence from the remaining arg
operands. No commands will be read from the standard
input.

-s If the -s flag is present or if no arguments remain,
commands are read from the standard input. Shell out-
put, except for the output of the Special Commands
listed above, is written to file descriptor 2.

-i If the -i flag is present or if the shell input and
output are attached to a terminal (as told by
ioctl(2)), then this shell is interactive. In this
case, TERM is ignored (so that kill 0 does not kill an
interactive shell) and INTR is caught and ignored (so
that wait is interruptible). In all cases, QUIT is
ignored by the shell.

-r If the -r flag is present the shell is a restricted
shell.

The remaining flags and arguments are described under the
set command above.

rksh Only
rksh is used to set up login names and execution environ-
ments whose capabilities are more controlled than those of
the standard shell. The actions of rksh are identical to
those of ksh, except that the following are disallowed:

+ changing directory (see cd(1))

+ setting the value of SHELL, ENV, or PATH

+ specifying path or command names containing /

+ redirecting output (>, >|, <>, and >>)

+ changing group (see newgrp(1)).

The restrictions above are enforced after .profile and the
ENV files are interpreted.

When a command to be executed is found to be a shell pro-
cedure, rksh invokes ksh to execute it. Thus, it is possi-
ble to provide to the end-user shell procedures that have
access to the full power of the standard shell, while impos-
ing a limited menu of commands; this scheme assumes that the
end-user does not have write and execute permissions in the
same directory.

The net effect of these rules is that the writer of the
.profile has complete control over user actions, by perform-
ing guaranteed setup actions and leaving the user in an
appropriate directory (probably not the login directory).

The system administrator often sets up a directory of com-
mands (that is, /usr/rbin) that can be safely invoked by
rksh.

ERRORS

Errors detected by the shell, such as syntax errors, cause
the shell to return a non-zero exit status. Otherwise, the
shell returns the exit status of the last command executed
(see also the exit command above). If the shell is being
used non-interactively then execution of the shell file is
abandoned. Run time errors detected by the shell are
reported by printing the command or function name and the
error condition. If the line number that the error occurred
on is greater than one, then the line number is also printed
in square brackets ([]) after the command or function name.

For a non-interactive shell, an error condition encountered
by a special built-in or other type of utility will cause
the shell to write a diagnostic message to standard error
and exit as shown in the following table:

_______________________________________________________________________
| Error Special Built-in Other Utilities|
| Shell language syntax error will exit will exit |
| Utility syntax error (option or will exit will not exit |
| operand error) |
| Redirection error will exit will not exit |
| Variable assignment error will exit will not exit |
| Expansion error will exit will exit |
| Command not found n/a may exit |
| Dot script not found will exit n/a |
|______________________________________________________________________|

An expansion error is one that occurs when the shell expan-
sions are carried out (for example, ${x!y}, because ! is not
a valid operator); an implementation may treat these as syn-
tax errors if it is able to detect them during tokenization,
rather than during expansion.

If any of the errors shown as "will (may) exit" occur in a
subshell, the subshell will (may) exit with a non-zero
status, but the script containing the subshell will not exit
because of the error.

In all of the cases shown in the table, an interactive shell
will write a diagnostic message to standard error without
exiting.

USAGE

See largefile(5) for the description of the behavior of ksh
and rksh when encountering files greater than or equal to 2
Gbyte ( 2**31 bytes).

EXIT STATUS

Each command has an exit status that can influence the
behavior of other shell commands. The exit status of com-
mands that are not utilities is documented in this section.
The exit status of the standard utilities is documented in
their respective sections.

If a command is not found, the exit status will be 127. If
the command name is found, but it is not an executable util-
ity, the exit status will be 126. Applications that invoke
utilities without using the shell should use these exit
status values to report similar errors.

If a command fails during word expansion or redirection, its
exit status will be greater than zero.

When reporting the exit status with the special parameter ?,
the shell will report the full eight bits of exit status
available. The exit status of a command that terminated
because it received a signal will be reported as greater
than 128.

FILES

/etc/profile"

/etc/suid_profile

$HOME/.profile

/tmp/sh*

/dev/null

ATTRIBUTES

See attributes(5) for descriptions of the following attri-
butes:

/usr/bin/ksh
/usr/bin/rksh"
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWcsu |
|_____________________________|_____________________________|
| CSI | Enabled |
|_____________________________|_____________________________|

/usr/xpg4/bin/ksh
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWxcu4 |
|_____________________________|_____________________________|
| CSI | Enabled |
|_____________________________|_____________________________|

ksh

NAME

SYNOPSIS

DESCRIPTION

Definitions

Commands

Comments

Aliasing

Tilde Substitution

Tilde Expansion

Command Substitution

Arithmetic Expansion

Process Substitution

Parameter Substitution

Parameter Expansion

Parameters Set by Shell

Variables Used by Shell

Blank Interpretation

File Name Generation

Quoting

Arithmetic Evaluation

Prompting

Conditional Expressions

Input/Output

Environment

Functions

Function Definition Command

Jobs

Signals

Execution

Command Re-entry

In-line Editing Option

Input Edit Commands

Motion Edit Commands

Search Edit Commands

Text Modification Edit Commands

Other Edit Commands

Special Commands

Invocation

ERRORS

USAGE

EXIT STATUS

FILES

ATTRIBUTES

SEE ALSO

WARNINGS

NOTES