ctags
CTAGS(1) CTAGS(1)
NAME
ctags - Generate tag files for source code
SYNOPSIS
ctags [options] [file(s)]
etags [options] [file(s)]
DESCRIPTION
The ctags and etags programs (hereinafter collectively
referred to as ctags, except where distinguished) generate
an index (or "tag") file for a variety of language objects
found in file(s). This tag file allows these items to be
quickly and easily located by a text editor or other util
ity. A "tag" signifies a language object for which an
index entry is available (or, alternatively, the index
entry created for that object).
Alternatively, ctags can generate a cross reference file
which lists, in human readable form, information about the
various source objects found in a set of language files.
Tag index files are supported by numerous editors, which
allow the user to locate the object associated with a name
appearing in a source file and jump to the file and line
which defines the name. Those known about at the time of
this release are:
Vi(1) and its derivatives (e.g. Elvis, Vim, Vile,
Lemmy), CRiSP, Emacs, FTE (Folding Text Editor), JED,
NEdit (Nirvana Edit), TSE (The SemWare Editor), X2,
Zeus
Ctags is capable of generating different kinds of tags for
each of many different languages. For a complete list of
supported languages, the names by which they are recog
nized, and the kinds of tags which are generated for each,
see TAG KINDS, below.
SOURCEFILES
Unless the --language-force option is specified, the lan
guage of each source file is automatically selected based
upon a mapping of file names to languages. On platforms
which support it, if the name of a file is not mapped to a
language and the file is executable, the first line of the
file is checked to see if the file is a "#!" script for a
recognized language. File names are mapped to languages
according to the following default mappings (which may be
overridden with the --langmap option):
Assembler
*.asm *.s *.S
ASP *.asp *.asa
Awk *.awk
C *.c
C++ *.C *.c++ *.cc *.cpp *.cxx *.h *.H *.hh *.hpp
*.hxx *.h++
BETA *.bet
COBOL *.cob *.COB
Eiffel *.e
Fortran *.f *.for *.ftn *.f77 *.f90 *.f95 *.F *.FOR
*.FTN *.F77 *.F90 *.F95
Java *.java
Lisp *.cl *.clisp *.el *.l *.lisp *.lsp *.ml
Make *.mak [Mm]akefile*
Pascal *.p *.pas
Perl *.pl *.pm *.perl
PHP *.php *.php3 *.phtml
Python *.py *.python
REXX *.cmd *.rexx *.rx
Ruby *.rb
Scheme *.sch *.scheme *.scm *.sm *.SCM *.SM
Shell scripts (Bourne/Korn/Z)
*.sh *.SH *.bsh *.bash *.ksh *.zsh
S-Lang *.sl
Tcl *.tcl *.wish
Vim *.vim
By default, all other files names are ignored. This per
mits running ctags on all files in either a single direc
tory (e.g. "ctags *"), or all files in an entire source
directory tree (e.g. "ctags -R"), since only those files
whose names are mapped to languages will be scanned.
The reason that .h extensions are mapped to C++ files
rather than C files is because it is common to use .h
extensions in C++, and no harm results in treating them as
C++ files.
OPTIONS
Despite the wealth of available options, defaults are set
so that ctags is most commonly executed without any
options (e.g. "ctags *", or "ctags -R"), which will create
a tag file in the current directory for all recognized
source files. The options described below are provided
merely to allow custom tailoring to meet special needs.
Note that spaces separating the single-letter options from
their parameters are optional.
Note also that the boolean parameters to the long form
options (those beginning with "--" and that take a
"[=yes|no]" parameter) may be omitted, in which case
"=yes" is implied. (e.g. --sort is equivalent to
--sort=yes). Note further that "=1" and "=on" are consid
ered synonyms for "=yes", and that "=0" and "=off" are
considered synonyms for "=no".
Some options are either ignored or useful only when used
while running in etags mode (see -e option). Such options
will be noted.
Most options may appear anywhere on the command line,
affecting only those files which follow the option. A few
options, however, must appear before the first file name
and will be noted as such.
Options taking language names will accept those names in
either upper or lower case. See TAG KINDS for a complete
list of the built-in language names.
-a Equivalent to --append.
-B Use backward searching patterns (e.g. ?pattern?).
[Ignored in etags mode]
-e Enable etags mode, which will create a tag file for
use with the Emacs editor. Alternatively, if ctags
is invoked by a name containing the string "etags"
(either by renaming, or creating a link to, the exe
cutable), etags mode will be enabled. This option
must appear before the first file name.
-f tagfile
Use the name specified by tagfile for the tag file
(default is "tags", or "TAGS" when running in etags
mode). If tagfile is specified as "-", then the tag
file is written to standard output instead. Ctags
will stubbornly refuse to take orders if tagfile
exists and its first line contains something other
than a valid tags line. This will save your neck if
you mistakenly type "ctags -f *.c", which would oth
erwise overwrite your first C file with the tags gen
erated by the rest! It will also refuse to accept a
multicharacter file name which begins with a '-'
(dash) character, since this most likely means that
you left out the tag file name and this option tried
to grab the next option as the file name. If you
really want to name your output tag file "-ugly",
specify it as "./-ugly". This option must appear
before the first file name. If this option is speci
fied more than once, only the last will apply.
-F Use forward searching patterns (e.g. /pattern/)
(default). [Ignored in etags mode]
-h list
Specifies a list of file extensions, separated by
periods, which are to be interpreted as include (or
header) files. To indicate files having no extension,
use a period not followed by a non-period character
(e.g. ".", "..x", ".x."). This option only affects
how the scoping of a particular kinds of tags is
interpreted (i.e. whether or not they are considered
as globally visible or visible only within the file
in which they are defined); it does not map the
extension to any particular language. Any tag which
is located in a non-include file and cannot be seen
(e.g. linked to) from another file is considered to
have file-limited (e.g. static) scope. No kind of tag
appearing in an include file will be considered to
have file-limited scope. If the first character in
the list is a plus sign, then the extensions in the
list will be appended to the current list; otherwise,
the list will replace the current list. See, also,
the --file-scope option. The default list is
".h.H.hh.hpp.hxx.h++.inc.def". To restore the default
list, specify -h default. Note that if an extension
supplied to this option is not already mapped to a
particular language (see SOURCE FILES, above), you
will also need to use either the --langmap or --lan
guage-force option.
-I tokenlist
Specifies a list of tokens which are to be specially
handled while parsing C and C++ source files. This
option is specifically provided to handle special
cases arising through the use of preprocessor macros.
When the tokens listed are simple tokens, these
tokens will be ignored during parsing of the source
files. If a token is suffixed with a '+' character,
ctags will also ignore any parenthesis-enclosed argu
ment list which may immediately follow the token in
the source files. If two tokens are separated with
the '=' character, the first token is replaced by the
second token for parsing purposes. The list of tokens
may be supplied directly on the command line or read
in from a separate file. If the first character of
tokenlist is '@', '.' or a pathname separator ('/' or
'\'), or the first two characters specify a drive
letter (e.g. "C:"), the parameter tokenlist will be
interpreted as a filename from which to read a list
of tokens, one per input line. Otherwise, tokenlist
is a list of tokens (or token pairs) to be specially
handled, each delimited by a either a comma or by
white space (in which case the list should be quoted
to keep the entire list as one command line argu
ment). Multiple -I options may be supplied. To clear
the list of ignore tokens, supply a single dash ("-")
for tokenlist.
This feature is useful when preprocessor macros are
used in such a way that they cause syntactic confu
sion due to their presence. Indeed, this is the best
way of working around a number of problems caused by
the presence of syntax-busting macros in source files
(see BUGS, below). Some examples will illustrate this
point.
int foo ARGDECL4(void *, ptr, long int, nbytes)
In the above example, the macro "ARGDECL4" would be
mistakenly interpreted to be the name of the function
instead of the correct name of "foo". Specifying -I
ARGDECL4 results in the correct behavior.
/* creates an RCS version string in module */
MODULE_VERSION("$Revision: 9.2 $")
In the above example the macro invocation looks too
much like a function definition because it is not
followed by a semicolon (indeed, it could even be
followed by a global variable definition that would
look much like a K&R style function parameter decla
ration). In fact, this seeming function definition
could possibly even cause the rest of the file to be
skipped over while trying to complete the definition.
Specifying -I MODULE_VERSION+ would avoid such a
problem.
CLASS Example {
// your content here
};
The example above uses "CLASS" as a preprocessor
macro which expands to something different for each
platform. For instance CLASS may be defined as "class
__declspec(dllexport)" on Win32 platforms and simply
"class" on UNIX. Normally, the absence of the C++
keyword "class" would cause the source file to be
incorrectly parsed. Correct behavior can be restored
by specifying -I CLASS=class.
-L file
Read from file a list of file names for which tags
should be generated. If file is specified as "-",
then file names are read from standard input. File
names read using this option are processed following
file names appearing on the command line. Options all
also accepted in this input. If this option is speci
fied more than once, only the last will apply. Note:
file is read in line-oriented mode, where a new line
is the only delimiter and spaces are considered sig
nificant, in order that file names containing spaces
may be supplied; this can affect how options are
parsed if included in the input.
-n Equivalent to --excmd=number.
-N Equivalent to --excmd=pattern.
-o tagfile
Equivalent to -f tagfile.
-R Equivalent to --recurse.
-u Equivalent to --sort=no (i.e. "unsorted").
-V Equivalent to --verbose.
-w This option is silently ignored for backwards compat
ibility with the ctags of SVR4 Unix.
-x Print a tabular, human-readable cross reference
(xref) file to standard output instead of generating
a tag file. The information contained in the output
includes: the tag name; the kind of tag; the line
number, file name, and source line (with extra white
space condensed) of the file which defines the tag.
No tag file is written and all options affecting tag
file output will be ignored. Example applications for
this feature are generating a listing of all func
tions located in a source file (e.g. ctags -x --c-
types=f file), or generating a list of all externally
visible global variables located in a source file
(e.g. ctags -x --c-types=v --file-scope=no file).
This option must appear before the first file name.
--append[=yes|no]
Indicates whether tags generated from the specified
files should be appended to those already present in
the tag file or should replace them. This option is
off by default. This option must appear before the
first file name. [Ignored in etags mode]
--etags-include=file
Include a reference to file in the tag file. This
option may be specified as many times as desired.
This supports Emacs' capability to use a tag file
which "includes" other tag files. [Used only in etags
mode]
--exclude=[pattern]
Add pattern to a list of excluded files and directo
ries. For each file name considered by ctags, pattern
will be compared against both the complete path (e.g.
some/path/base.ext) and the base name (e.g. base.ext)
of the file, thus allowing patterns which match a
given file name irrespective of its path, or match
only a specific path. If appropriate support is
available from the runtime library of your C com
piler, then pattern may contain the usual shell wild
cards common on Unix (be sure to quote the option
parameter to protect the wildcards from being
expanded by the shell before being passed to ctags;
also be aware that wildcards can match the slash
character, '/'). You can determine if shell wildcards
are available on your platfom by examining the output
of the --version option, which will include "+wild
cards" in the compiled feature list; otherwise, pat
tern is matched against file names using a simple
textual comparison.
If pattern begins with the character '@', then the
rest of the string is interpreted as a file name from
which to read exclusion patterns, one per line. If
pattern is empty, the list of excluded patterns is
cleared. Note that at program startup, the exclude
list contains "EIFGEN" and "SCCS" by default, which
are directories for which it is generally not desir
able to descend.
--excmd=type
Determines the type of EX command used to locate tags
in the source file. [Ignored in etags mode]
The valid values for type (either the entire word or
the first letter is accepted) are:
number Use only line numbers in the tag file for
locating tags. This has four advantages:
1. Significantly reduces the size of the
resulting tag file.
2. Eliminates failures to find tags because
the line defining the tag has changed,
causing the pattern match to fail (note
that some editors, such as vim, are able
to recover in many such instances).
3. Eliminates finding identical matching,
but incorrect, source lines (see BUGS,
below).
4. Retains separate entries in the tag file
for lines which are identical in con
tent. In pattern mode, duplicate entries
are dropped because the search patterns
they generate are identical, making the
duplicate entries useless.
However, this option has one significant
drawback: changes to the source files can
cause the line numbers recorded in the tag
file to no longer correspond to the lines in
the source file, causing jumps to some tags
to miss the target definition by one or more
lines. Basically, this option is best used
when the source code to which it is applied
is not subject to change. Selecting this
option type causes the following options to
be ignored: -BF.
pattern Use only search patterns for all tags,
rather than the line numbers usually used
for macro definitions. This has the advan
tage of not referencing obsolete line num
bers when lines have been added or removed
since the tag file was generated.
mixed In this mode, patterns are generally used
with a few exceptions. For C, line numbers
are used for macro definition tags. This was
the default format generated by the original
ctags and is, therefore, retained as the
default for this option. For Fortran, line
numbers are used for common blocks because
their corresponding source lines are gener
ally identical, making pattern searches use
less for finding all matches.
--extra=[+|-]flags
Specifies whether to include extra tag entries for
certain kinds of information. The parameter flags is
a set of one-letter flags, each representing one kind
of extra tag entry to include in the tag file. If
flags is preceded by by either the '+' or '-' charac
ter, the effect of each flag is added to, or removed
from, those currently enabled; otherwise the flags
replace any current settings. The meaning of each
flag is as follows:
f Include an entry for the base file name of
every source file (e.g. "example.c"), which
addresses the first line of the file.
q Include an extra class-qualified tag entry for
each tag which is a member of a class (for
languages for which this information is
extracted; currently C++, Eiffel, and Java).
The actual form of the qualified tag depends
upon the language from which the tag was
derived (using a form that is most natural for
how qualified calls are specified in the lan
guage). For C++, it is in the form
"class::member"; for Eiffel and Java, it is in
the form "class.member". This may allow easier
location of a specific tags when multiple
occurrances of a tag name occur in the tag
file. Note, however, that this could poten
tially more than double the size of the tag
file.
--fields=[+|-]flags
Specifies the available extension fields which are to
be included in the entries of the tag file (see TAG
FILE FORMAT, below, for more information). The param
eter flags is a set of one-letter flags, each repre
senting one type of extension field to include, with
the following meanings (disabled by default unless
indicated):
a Access (or export) of class members
f File-restricted scoping [enabled]
i Inheritance information
k Kind of tag as a single letter [enabled]
K Kind of tag as full name
l Language of source file containing tag
m Implementation information
n Line number of tag definintion
s Scope of tag definition [enabled]
z Include the "kind:" key in kind field
Each letter or group of letters may be preceded by
either '+' to add it to the default set, or '-' to
exclude it. In the absence of any preceding '+' or
'-' sign, only those kinds explicitly listed in flags
will be included in the output (i.e. overriding the
default set). This option is ignored if the option
--format=1 has been specified.
--file-scope[=yes|no]
Indicates whether tags scoped only for a single file
(i.e. tags which cannot be seen outside of the file
in which they are defined, such as "static" tags)
should be included in the output. See, also, the -h
option. This option is enabled by default.
--filter[=yes|no]
Causes ctags to behave as a filter, reading source
file names from standard input and printing their
tags to standard output on a file-by-file basis. If
--sorted is enabled, tags are sorted only within the
source file in which they are defined. File names are
read from standard output in line-oriented input mode
(see note for -L option) and only after file names
listed on the command line or from any file supplied
using the -L option. When this option is enabled, the
options -f, -o, and --totals are ignored. This option
is quite esoteric and is disabled by default. This
option must appear before the first file name.
--filter-terminator=string
Specifies a string to print to standard output
following the tags for each file name parsed when the
--filter option is enabled. This may permit an appli
cation reading the output of ctags to determine when
the output for each file is finished. Note that if
the file name read is a directory and --recurse is
enabled, this string will be printed only one once at
the end of all tags found for by descending the
directory. This string will always be separated from
the last tag line for the file by its terminating
newline. This option is quite esoteric and is empty
by default. This option must appear before the first
file name.
--format=level
Change the format of the output tag file. Currently
the only valid values for level are 1 or 2. Level 1
specifies the original tag file format and level 2
specifies a new extended format containing extension
fields (but in a manner which retains backward com
patibility with original vi(1) implementations). The
default level is 2. This option must appear before
the first file name. [Ignored in etags mode]
--help
Prints to standard output a detailed usage descrip
tion.
--if0[=yes|no]
Indicates a preference as to whether code within an
"#if 0" branch of a preprocessor conditional should
be examined for non-macro tags (macro tags are always
included). Because the intent of this construct is to
disable code, the default value of this options is
no. Note that this indicates a preference only and
does not guarantee skipping code within an "#if 0"
branch, since the fall-back algorithm used to gener
ate tags when preprocessor conditionals are too com
plex follows all branches of a conditional. This
option is disabled by default.
--<LANG>-types=[+|-]kinds
Specifies a list of language-specific kinds of tags
(or kinds) to include in the output file for a par
ticular language, where <LANG> is one of the built-in
language names (see TAG KINDS, below, for a complete
list). The parameter kinds is a group of one-letter
flags designating kinds of tags (particular to the
language) to either include or exclude from the out
put. The specific sets of flags recognized for each
language, their meanings and defaults is described in
TAG KINDS, below. Each letter or group of letters may
be preceded by either '+' to add it to the default
set, or '-' to exclude it. In the absence of any pre
ceding '+' or '-' sign, only those kinds explicitly
listed in kinds will be included in the output (i.e.
overriding the default for the specified language).
As an example for the C language, in order to add
prototypes and external variable declarations to the
default set of tag kinds, but exclude macros, use
--c-types=+px-d; to include only tags for functions,
use --c-types=f.
--langdef=name
Defines a new user-defined language, name, to be
parsed with regular expressions. Once defined, name
may be used in other options taking language names.
The typical use of this option is to first define the
language, then map file names to it using --langmap,
then specify regular expressions using --regex-<LANG>
to define how its tags are found.
--langmap=map[,map[...]]
Controls how file names are mapped to languages (see
SOURCE FILES, above). Each comma-separated map con
sists of the language name (either a built-in or
user-defined language), a colon, and a list of file
extensions and/or file name patterns. A file exten
sion is specified by preceding the extension with a
period (e.g. ".c"). A file name pattern is specified
by enclosing the pattern in parentheses (e.g.
"([Mm]akefile)"). If appropriate support is available
from the runtime library of your C compiler, then the
file name pattern may contain the usual shell wild
cards common on Unix (be sure to quote the option
parameter to protect the wildcards from being
expanded by the shell before being passed to ctags).
You can determine if shell wildcards are available on
your platfom by examining the output of the --version
option, which will include "+wildcards" in the com
piled feature list; otherwise, the file name patterns
are matched against file names using a simple textual
comparison.
If the first character in a map is a plus sign, then
the extensions and file name patterns in that map
will be appended to the current map for that lan
guage; otherwise, the map will replace the current
map. For example, to specify that only files with
extensions of .c and .x are to be treated as C lan
guage files, use "--langmap=c:.c.x"; to also add
files with extensions of .j as Java language files,
specify "--langmap=c:.c.x,java:+.j". To map makefiles
(.e.g files named either "Makefile", "makefile", or
having the extension ".mak") to a language called
"make", specify "--langmap=make:([Mm]akefile).mak".
To map files having no extension, specify a period
not followed by a non-period character (e.g. ".",
"..x", ".x."). To clear the mapping for a particular
language (thus inhibiting automatic generation of
tags for that language), specify an empty extension
list (e.g. "--langmap=fortran:"). To restore the
default language mappings for all a particular lan
guage, supply the keyword "default" for the mapping.
To specify restore the default language mappings for
all languages, specify "--langmap=default". Note that
file extensions are tested before file name patterns
when inferring the language of a file.
--language-force=language
By default, ctags automatically selects the language
of a source file, ignoring those files whose language
cannot be determined (see SOURCE FILES, above). This
option forces the specified language (either built-in
or user-defined) to be used for every supplied file
instead of automatically selecting the language based
upon its extension. In addition, the special value
auto indicates that the language should be automati
cally selected (which effectively disables this
option).
--languages=[+|-]list
Specifies the languages for which tag generation is
enabled, with list containing a comma-separated list
of language names (either built-in or user-defined).
If the first language of list is not preceded by
either a languages in list. Until a '-' is encoun
tered, each language in the list will be added to the
current list. As either the '+' or '-' is encountered
in the list, the languages following it are added or
removed from the current list, respectively. Thus, it
becomes simple to replace the current list with a new
one, or to add or remove languages from the current
list. The actual list of files for which tags will be
generated depends upon the language extension mapping
in effect (see the --langmap option). Note that all
languages, including user-defined languages are
enabled unless explicitly disabled using this option.
Language names included in list may be any built-in
language or one previously defined with --langdef.
The default is "all", which is also accepted as a
valid argument. See TAG KINDS for a complete list of
the built-in language names.
--license
Prints a summary of the software license to standard
output.
--line-directives[=yes|no]
Specifies whether "#line" directives should be recog
nized. These are present in the output of preproces
sors and contain the line number, and possibly the
file name, of the original source file(s) from which
the preprocessor output file was generated. When
enabled, this option will cause ctags to generate tag
entries marked with the file names and line numbers
of their locations original source file(s), instead
of their actual locations in the preprocessor output.
The actual file names placed into the tag file will
have the same leading path components as the prepro
cessor output file, since it is assumed that the
original source files are located relative to the
preprocessor output file (unless, of course, the
#line directive specifies an absolute path). This
option is off by default. Note: This option is gener
ally only useful when used together with the
--excmd=number (-n) option. Also, you may have to use
either the --langmap or --language-force option if
the extension of the preprocessor output file is not
known to ctags.
--links[=yes|no]
Indicates whether symbolic links (if supported)
should be followed. When disabled, symbolic links are
ignored. This option is on by default.
--options=file
Read additional options from file.
--recurse[=yes|no]
Recurse into directories encountered in the list of
supplied files. If the list of supplied files is
empty and no file list is specified with the -L
option, then the current directory (i.e. ".") is
assumed. Symbolic links are followed. If you don't
like these behaviors, either explicitly specify the
files or pipe the output of find(1) into ctags -L-
instead. Note: This option is not supported on all
platforms at present. It is available if the output
of the --help option includes this option. See,
also, the --exclude to limit recursion.
--regex-<LANG>=/regexp/replacement/[kind-spec/][flags]
The /regexp/replacement/ pair define a regular
expression replacement pattern, similar in style to
sed substitution commands, with which to generate
tags from source files mapped to the named language,
<LANG>, (either a built-in or user-defined language).
The regular expression regexp defines a regular
expression which is used to locate a single source
line containing a tag and may specify tab characters
using \t. When a matching line is found, a tag will
be generated for the name defined by replacement,
which generally will contain the special back-refer
ences \1 through \9 to refer to matching sub-expres
sion groups within regexp. The '/' separator charac
ters shown in the parameter to the option can actu
ally be replaced by any character. Note that
whichever separator character is used will have to be
escaped with a backslash ('\') character wherever it
is used in the parameter as something other than a
separator. The regular expression defined by this
option is added to the current list of regular
expressions for the specified language unless the
parameter is omitted, in which case the current list
is cleared.
Unless modified by flags, regexp is interpreted as a
Posix extended regular expression. The replacement
should expand for all matching lines to a non-empty
string of characters, or a warning message will be
reported. An optional kind specifier for tags match
ing regexp may follow replacement, which will deter
mine what kind of tag is reported in the "kind"
extension field (see TAG FILE FORMAT, below). The
kind-spec is expected to be in the form of a single
letter, a comma, and a name followed by a separator,
which specify the short and long forms of the kind
value. If kind-spec is omitted, it defaults to
"r,regex". Finally, flags are one or more single-
letter characters having the following effect upon
the interpretation of regexp:
b The pattern is interpreted as a Posix basic
regular expression.
e The pattern is interpreted as a Posix extended
regular expression (default).
i The regular expression is to be applied in a
case-insensitive manner.
Note that this option is available only if ctags was
compiled with support for regular expressions, which
depends upon your platform. You can determine if sup
port for regular expressions is compiled in by exam
ining the output of the --version option, which will
include "+regex" in the compiled feature list.
--sort[=yes|no]
Indicates whether the tag file should be sorted on
the tag name (default is yes). Note that the original
vi(1) requires sorted tags. This option is on by
default. This option must appear before the first
file name. [Ignored in etags mode]
--tag-relative[=yes|no]
Indicates that the file paths recorded in the tag
file should be relative to the directory containing
the tag file, rather than relative to the current
directory, unless the files supplied on the command
line are specified with absolute paths. This option
must appear before the first file name. The default
is yes when running in etags mode (see the -e
option), no otherwise.
--totals[=yes|no]
Prints statistics about the source files read and the
tag file written during the current invocation of
ctags. This option is off by default. This option
must appear before the first file name.
--verbose[=yes|no]
Enable verbose mode. This prints out information on
option processing and a brief message describing what
action is being taken for each file considered by
ctags. Normally, ctags does not read command line
arguments until after options are read from the con
figuration files (see FILES, below) and the CTAGS
environment variable. However, if this option is the
first argument on the command line, it will take
effect before any options are read from these
sources. The default is no.
--version
Prints a version identifier for ctags to standard
output. This is guaranteed to always contain the
string "Exuberant Ctags".
TAG KINDS
Each type (or kind) of tag recorded in the tag file is
indicated by a one-letter flag, which is also used to fil
ter the tags placed into the output through use of the
--<LANG>-type option. The flags corresponding to each tag
kind for each langauge are described below. Note that some
languages and/or tag kinds may be implemented using regu
lar expressions and may not be available if regex support
is not compiled into ctags (see the --regex-<LANG>
option). Kinds are enabled by default except where noted
(with "[off]").
Asm
d defines
l labels
m macros
ASP
f functions
s subroutines
Awk
f functions
BETA
f fragment definitions
p all patterns [off]
s slots (fragment uses)
v patterns (only virtual or rebound patterns are
recorded)
C and C++
c classes
d macro definitions (and #undef names)
e enumerators
f function definitions
g enumeration names
m class, struct, or union members
n namespaces
p function prototypes and declarations [off]
s structure names
t typedefs
u union names
v variable definitions
x extern and forward variable declarations [off]
Cobol
p paragraphs
Eiffel
c classes
f features
l local entities [off]
Fortran
b block data
c common blocks
e entry points
f functions
i interfaces
k type components
l labels
L local and common block variables [off]
m modules
n namelists
p programs
s subroutines
t derived types
v module variables
Java
c classes
f fields
i interfaces
m methods
p packages
Lisp
f functions
Make
m macros
Pascal
f functions
p procedures
Perl
s subroutines
PHP
c classes
f functions
Python
c classes
f functions
REXX
s subroutines
Ruby
c classes
f functions
m mixins
Scheme
f functions
s sets
Sh (Bourne, Korn, Z)
f functions
SLang
f functions
n namespaces
Tcl
p procedures
Vim
f functions
OPERATIONAL DETAILS
As ctags considers each file name in turn, it tries to
determine the language of the file by applying the follow
ing three tests in order: if the file extension has been
mapped to a language, if the file name matches a shell
pattern mapped to a language, and finally if the file is
executable and its first line specifies an interpreter
using the Unix-style "#!" specification (if supported on
the platform). If a language was identified, the file is
opened and then the appropriate language parser is called
to operate on the currently open file. The parser parses
through the file and adds an entry to the tag file for
each language object it is written to handle. See TAG FILE
FORMAT, below, for details on these entries.
This implementation of ctags imposes no formatting
requirements on C code as do legacy implementations. Older
implementations of ctags tended to rely upon certain for
matting assumptions in order to help it resolve coding
dilemmas caused by preprocessor conditionals.
In general, ctags tries to be smart about conditional pre
processor directives. If a preprocessor conditional is
encountered within a statement which defines a tag, ctags
follows only the first branch of that conditional (except
in the special case of "#if 0", in which case it follows
only the last branch). The reason for this is that failing
to pursue only one branch can result in ambiguous syntax,
as in the following example:
#ifdef TWO_ALTERNATIVES
struct {
#else
union {
#endif
short a;
long b;
}
Both branches cannot be followed, or braces become unbal
anced and ctags would be unable to make sense of the syn
tax.
If the application of this heuristic fails to properly
parse a file, generally due to complicated and inconsis
tent pairing within the conditionals, ctags will retry the
file using a different heuristic which does not selec
tively follow conditional preprocessor branches, but
instead falls back to relying upon a closing brace ("}")
in column 1 as indicating the end of a block once any
brace imbalance results from following a #if conditional
branch.
Ctags will also try to specially handle arguments lists
enclosed in double sets of parentheses in order to accept
the following conditional construct:
extern void foo __ARGS((int one, char two));
Any name immediately preceding the "((" will be automati
cally ignored and the previous name will be used.
C++ operator definitions are specially handled. In order
for consistency with all types of operators (overloaded
and conversion), the operator name in the tag file will
always be preceded by the string "operator " (i.e. even if
the actual operator definition was written as "opera
tor<<").
After creating or appending to the tag file, it is sorted
by the tag name, removing identical tag lines.
TAG FILE FORMAT
When not running in etags mode, each entry in the tag file
consists of a separate line, each looking like this in the
most general case:
tag_name<TAB>file_name<TAB>ex_cmd;"<TAB>extension_fields
The fields and separators of these lines are specified as
follows:
1. tag name
2. single tab character
3. name of the file in which the object associated
with the tag is located
4. single tab character
5. EX command used to locate the tag within the file;
generally a search pattern (either /pattern/ or
?pattern?) or line number (see --excmd). Tag file
format 2 (see --format) extends this EX command
under certain circumstances to include a set of
extension fields (described below) embedded in an
EX comment immediately appended to the EX command,
which leaves it backwards compatible with original
vi(1) implementations.
A few special tags are written into the tag file for
internal purposes. These tags are composed in such a way
that they always sort to the top of the file. Therefore,
the first two characters of these tags are used a magic
number to detect a tag file for purposes of determining
whether a valid tag file is being overwritten rather than
a source file.
Note that the name of each source file will be recorded in
the tag file exactly as it appears on the command line.
Therefore, if the path you specified on the command line
was relative to the current directory, then it will be
recorded in that same manner in the tag file. See, how
ever, the --tag-relative option for how this behavior can
be modified.
Extension fields are tab-separated key-value pairs
appended to the end of the EX command as a comment, as
described above. These key value pairs appear in the gen
eral form "key:value". Their presence in the lines of the
tag file are controlled by the --fields option. The possi
ble keys and the meaning of their values are as follows:
access Indicates the visibility of this class member,
where value is specific to the language.
file Indicates that the tag has file-limited visi
bility. This key has no corresponding value.
kind Indicates the type, or kind, of tag. Its value
is either one of the corresponding one-letter
flags described under the various
--<LANG>-types options above, or a full name.
It is permitted (and is, in fact, the default)
for the key portion of this field to be omit
ted. The optional behaviors are controlled
with the --fields option.
implementation
When present, this indicates a limited imple
mentation (abstract vs. concrete) of a routine
or class, where value is specific to the lan
guage ("virtual" or "pure virtual" for C++;
"abstract" for Java).
inherits When present, value. is a comma-separated list
of classes from which this class is derived
(i.e. inherits from).
In addition, information on the scope of the tag defini
tion may be available, with the key portion equal to some
language-dependent construct name and its value the name
declared for that construct in the program. This scope
entry indicates the scope in which the tag was found. For
example, a tag generated for a C structure member would
have a scope looking like "struct:myStruct".
HOW TO USE WITH VI
Vi will, by default, expect a tag file by the name "tags"
in the current directory. Once the tag file is built, the
following commands exercise the tag indexing feature:
vi -t tag Start vi and position the cursor at the file
and line where "tag" is defined.
:ta tag Find a tag.
Ctrl-] Find the tag under the cursor.
Ctrl-T Return to previous location before jump to tag
(not widely implemented).
HOW TO USE WITH GNU EMACS
Emacs will, by default, expect a tag file by the name
"TAGS" in the current directory. Once the tag file is
built, the following commands exercise the tag indexing
feature:
Meta-x <RET> FILE <RET>
Display a list of the tags defined in the pro
gram file FILE.
Meta-. [TAG] <RET>
Find the first definition of TAG (default is
identifier under cursor). The default tag is
the identifier under the cursor.
C-u M-. Find the next definition for the last tag.
For more commands, see the Tags topic in the Emacs info
document.
CAVEATS
Because ctags is neither a preprocessor nor a compiler,
use of preprocessor macros can fool ctags into either
missing tags or improperly generating inappropriate tags.
Although ctags has been designed to handle certain common
cases, this is the single biggest cause of reported prob
lems. In particular, the use of preprocessor constructs
which alter the textual syntax of C can fool ctags. You
can work around many such problems by using the -I option.
White space is treated as a separator for file names and
options read from list files, specified using the -L
option, and in filter mode (specified using the --filter
option). Therefore, it is not currently possible to supply
file names or other options containing embedded white
space (spaces, etc.) through these options.
Note that when ctags generates uses patterns for locating
tags (see the --excmd option), it is entirely possible
that the wrong line may be found by your editor if there
exists another source line which is identical to the line
containing the tag. The following example demonstrates
this condition:
int variable;
/* ... */
void foo(variable)
int variable;
{
/* ... */
}
Depending upon which editor you use and where in the code
you happen to be, it is possible that the search pattern
may locate the local parameter declaration in foo() before
it finds the actual global variable definition, since the
lines (and therefore their search patterns are identical).
This can be avoided by use of the --excmd=n option.
BUGS
Ctags has more options than ls(1).
When parsing a C++ member function definition (e.g.
"className::function"), ctags cannot determine whether the
scope specifier is a class name or a namespace specifier
and always lists it as a class name in the scope portion
of the extension fields. Also, if the function defintion
is located in a separate file from than where the class is
defined (the usual case), the access specification (i.e.
public, protected, or private) that the function had when
declared in the class is not known.
No qualified tags are generated for language objects
inherited into a class.
ENVIRONMENT VARIABLES
CTAGS If this environment variable exists, it will be
expected to contain a set of default options which
are read when ctags starts, after the configura
tion files listed in FILES, below, are read, but
before any command line options are read. Options
appearing on the command line will override
options specified in this file. Only options will
be read from this file. Note that all white space
in this variable in considered a separator, making
it impossible to pass an option parameter contain
ing an embedded space. If this is a problem, use
a configuration file instead.
ETAGS Similar to the CTAGS variable above, this vari
able, if found, will be read when etags starts. If
this variable is not found, etags will try to use
CTAGS instead.
TMPDIR On Unix-like hosts where mkstemp() is available,
the value of this variable specifies the directory
in which to place temporary files. This can be
useful if the size of a temporary file becomes too
large to fit on the partition holding the default
temporary directory defined at compilation time.
ctags creates temporary files only if either (1)
an emacs-style tag file is being generated, (2)
the tag file is being sent to standard output, or
(3) the program was compiled to use an internal
sort algorithm to sort the tag files instead of
the the sort utility of the operating system. If
the sort utility of the operating system is being
used, it will generally observe this variable
also. Note that if ctags is setuid, the value of
TMPDIR will be ignored.
FILES
/etc/ctags.conf
/usr/local/etc/ctags.conf
$HOME/.ctags
.ctags
If any of these configuration files exist, each
will be expected to contain a set of default
options which are read in the order listed when
ctags starts, but before the CTAGS environment
variable is read or any command line options are
read. This makes it possible to set up site-wide,
personal or project-level defaults. It is possible
to compile ctags to read an additional configura
tion file immediately before $HOME/.ctags, which
will be indicated if the output produced by the
--version option lists the "custom-conf" feature.
Options appearing in the CTAGS environment variable
or on the command line will override options speci
fied in these files. Only options will be read from
these files. Note that the option files are read in
line-oriented mode in which spaces are significant
(since shell quoting is not possible). Each line of
the file is read as one command line parameter (as
if it were quoted with single quotes). Therefore,
use new lines to indicate separate command-line
arguments.
tags The default tag file created by ctags.
TAGS The default tag file created by etags.
SEE ALSO
The official Exuberant Ctags web site at:
http://ctags.sourceforge.net
Also ex(1), vi(1), elvis, or, better yet, vim, the offi
cial editor of ctags. For more information on vim, see the
VIM Pages web site at:
http://www.vim.org/
AUTHOR
Darren Hiebert <darren@hiebert.com>,
<dhiebert@users.sourceforge.net>
http://darren.hiebert.com/
MOTIVATION
"Think ye at all times of rendering some service to every
member of the human race."
"All effort and exertion put forth by man from the full
ness of his heart is worship, if it is prompted by the
highest motives and the will to do service to humanity."
-- From the Baha'i Writings
CREDITS
This version of ctags was originally derived from and
inspired by the ctags program by Steve Kirkendall <kirk
enda@cs.pdx.edu> that comes with the Elvis vi clone
(though virtually none of the original code remains).
Credit is also due Bram Moolenaar <Bram@vim.org>, the
author of vim, who has devoted so much of his time and
energy both to developing the editor as a service to oth
ers, and to helping the orphans of Uganda.
The section entitled "HOW TO USE WITH GNU EMACS" was
shamelessly stolen from the info page for GNU etags.
Darren Hiebert Version 5.0.1 CTAGS(1)