diff

 

---

 DIFF(1)                     GNU Tools                     DIFF(1)
 
 
 
NAME
        diff - find differences between two files
 
SYNOPSIS
        diff [options] from-file to-file
 
DESCRIPTION
        In  the  simplest  case, diff compares the contents of the
        two files from-file and to-file.  A file name of -  stands
        for text read from the standard input.  As a special case,
        diff - - compares a copy of standard input to itself.
 
        If from-file is a directory and to-file is not, diff  com­
        pares the file in from-file whose file name is that of to-
        file, and vice versa.  The non-directory file must not  be
        -.
 
        If  both  from-file and to-file are directories, diff com­
        pares corresponding files in both directories,  in  alpha­
        betical order; this comparison is not recursive unless the
        -r or --recursive option is given.   diff  never  compares
        the  actual  contents of a directory as if it were a file.
        The file that is  fully  specified  may  not  be  standard
        input,  because  standard input is nameless and the notion
        of ``file with the same name'' does not apply.
 
        diff options begin with -, so normally from-file  and  to-
        file  may not begin with -.  However, -- as an argument by
        itself treats the remaining arguments as file  names  even
        if they begin with -.
 
    Options
        Below  is  a  summary  of all of the options that GNU diff
        accepts.  Most options have two equivalent names,  one  of
        which  is  a single letter preceded by -, and the other of
        which is a long name preceded by --.  Multiple single let­
        ter options (unless they take an argument) can be combined
        into a single command line word: -ac is equivalent  to  -a
        -c.   Long  named options can be abbreviated to any unique
        prefix of their name.  Brackets ([ and ]) indicate that an
        option takes an optional argument.
 
        -lines Show  lines  (an  integer)  lines of context.  This
               option does not specify an output format by itself;
               it  has  no effect unless it is combined with -c or
               -u.  This option is obsolete.   For  proper  opera­
               tion,  patch  typically needs at least two lines of
               context.
 
        -a     Treat all files as text and compare  them  line-by-
               line, even if they do not seem to be text.
 
        -b     Ignore changes in amount of white space.
 
        -B     Ignore  changes  that  just  insert or delete blank
               lines.
 
        --brief
               Report only  whether  the  files  differ,  not  the
               details of the differences.
 
        -c     Use the context output format.
 
        -C lines
        --context[=lines]
               Use  the  context  output format, showing lines (an
               integer) lines of context, or three if lines is not
               given.  For proper operation, patch typically needs
               at least two lines of context.
 
        --changed-group-format=format
               Use format to output a line group  containing  dif­
               fering  lines  from both files in if-then-else for­
               mat.
 
        -d     Change the algorithm to perhaps find a smaller  set
               of changes.  This makes diff slower (sometimes much
               slower).
 
        -D name
               Make merged if-then-else format output, conditional
               on the preprocessor macro name.
 
        -e
        --ed   Make output that is a valid ed script.
 
        --exclude=pattern
               When comparing directories, ignore files and subdi­
               rectories whose basenames match pattern.
 
        --exclude-from=file
               When comparing directories, ignore files and subdi­
               rectories  whose  basenames  match any pattern con­
               tained in file.
 
        --expand-tabs
               Expand tabs to spaces in the  output,  to  preserve
               the alignment of tabs in the input files.
 
        -f     Make  output  that  looks vaguely like an ed script
               but has changes in the order  they  appear  in  the
               file.
 
        -F regexp
               In  context  and  unified  format, for each hunk of
               differences, show some of the last  preceding  line
               that matches regexp.
 
        --forward-ed
               Make  output  that  looks vaguely like an ed script
               but has changes in the order  they  appear  in  the
               file.
 
        -h     This  option currently has no effect; it is present
               for Unix compatibility.
 
        -H     Use heuristics to speed  handling  of  large  files
               that have numerous scattered small changes.
 
        --horizon-lines=lines
               Do  not  discard the last lines lines of the common
               prefix and the first lines lines of the common suf­
               fix.
 
        -i     Ignore  changes in case; consider upper- and lower-
               case letters equivalent.
 
        -I regexp
               Ignore changes that just  insert  or  delete  lines
               that match regexp.
 
        --ifdef=name
               Make merged if-then-else format output, conditional
               on the preprocessor macro name.
 
        --ignore-all-space
               Ignore white space when comparing lines.
 
        --ignore-blank-lines
               Ignore changes that just  insert  or  delete  blank
               lines.
 
        --ignore-case
               Ignore  changes in case; consider upper- and lower-
               case to be the same.
 
        --ignore-matching-lines=regexp
               Ignore changes that just  insert  or  delete  lines
               that match regexp.
 
        --ignore-space-change
               Ignore changes in amount of white space.
 
        --initial-tab
               Output a tab rather than a space before the text of
               a line in normal or context  format.   This  causes
               the alignment of tabs in the line to look normal.
 
        -l     Pass the output through pr to paginate it.
 
        -L label
        --label=label
               Use  label  instead of the file name in the context
               format and unified format headers.
 
        --left-column
               Print only the left column of two common  lines  in
               side by side format.
 
        --line-format=format
               Use  format  to  output all input lines in in-then-
               else format.
 
        --minimal
               Change the algorithm to perhaps find a smaller  set
               of changes.  This makes diff slower (sometimes much
               slower).
 
        -n     Output RCS-format diffs; like -f except  that  each
               command specifies the number of lines affected.
 
        -N
        --new-file
               In directory comparison, if a file is found in only
               one directory, treat it as present but empty in the
               other directory.
 
        --new-group-format=format
               Use  format  to  output a group of lines taken from
               just the second file in if-then-else format.
 
        --new-line-format=format
               Use format to output a line  taken  from  just  the
               second file in if-then-else format.
 
        --old-group-format=format
               Use  format  to  output a group of lines taken from
               just the first file in if-then-else format.
 
        --old-line-format=format
               Use format to output a line  taken  from  just  the
               first file in if-then-else format.
 
        -p     Show which C function each change is in.
 
        -P     When  comparing directories, if a file appears only
               in the second directory of the  two,  treat  it  as
               present but empty in the other.
 
        --paginate
               Pass the output through pr to paginate it.
 
        -q     Report  only  whether  the  files  differ,  not the
               details of the differences.
 
        -r     When comparing directories, recursively compare any
               subdirectories found.
 
        --rcs  Output  RCS-format  diffs; like -f except that each
               command specifies the number of lines affected.
 
        --recursive
               When comparing directories, recursively compare any
               subdirectories found.
 
        --report-identical-files
        -s     Report when two files are the same.
 
        -S file
               When  comparing  directories,  start  with the file
               file.  This is used for resuming an aborted compar­
               ison.
 
        --from-file=file
               Compare file to all operands.  file can be a direc­
               tory.
 
        --to-file=file
               Compare all operands to file. file can be a  direc­
               tory.
 
        --sdiff-merge-assist
               Print  extra information to help sdiff.  sdiff uses
               this option when it runs diff.  This option is  not
               intended for users to use directly.
 
        --show-c-function
               Show which C function each change is in.
 
        --show-function-line=regexp
               In  context  and  unified  format, for each hunk of
               differences, show some of the last  preceding  line
               that matches regexp.
 
        --side-by-side
               Use the side by side output format.
 
        --speed-large-files
               Use  heuristics  to  speed  handling of large files
               that have numerous scattered small changes.
 
        --starting-file=file
               When comparing directories,  start  with  the  file
               file.  This is used for resuming an aborted compar­
               ison.
 
        --suppress-common-lines
               Do not print common lines in side by side format.
 
        -t     Expand tabs to spaces in the  output,  to  preserve
               the alignment of tabs in the input files.
 
        -T     Output a tab rather than a space before the text of
               a line in normal or context  format.   This  causes
               the alignment of tabs in the line to look normal.
 
        --text Treat  all  files as text and compare them line-by-
               line, even if they do not appear to be text.
 
        -u     Use the unified output format.
 
        --unchanged-group-format=format
               Use format to output a group of common lines  taken
               from both files in if-then-else format.
 
        --unchanged-line-format=format
               Use format to output a line common to both files in
               if-then-else format.
 
        --unidirectional-new-file
               When comparing directories, if a file appears  only
               in  the  second  directory  of the two, treat it as
               present but empty in the other.
 
        -U lines
        --unified[=lines]
               Use the unified output format,  showing  lines  (an
               integer) lines of context, or three if lines is not
               given.  For proper operation, patch typically needs
               at least two lines of context.
 
        -v
        --version
               Output the version number of diff.
 
        -w     Ignore white space when comparing lines.
 
        -W columns
        --width=columns
               Use an output width of columns in side by side for­
               mat.
 
        -x pattern
               When comparing directories, ignore files and subdi­
               rectories whose basenames match pattern.
 
        -X file
               When comparing directories, ignore files and subdi­
               rectories whose basenames match  any  pattern  con­
               tained in file.
 
        -y     Use the side by side output format.
 
SEE ALSO
        cmp(1),   comm(1),   diff3(1),   ed(1),  patch(1),  pr(1),
        sdiff(1).
 
 DIAGNOSTICS
        An exit status of 0 means no  differences  were  found,  1
        means some differences were found, and 2 means trouble.
 
 
 
 GNU Tools                   22sep1993                     DIFF(1)

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