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DIFF(1)

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NAME    [Toc]    [Back]

       diff - find differences between two files

SYNOPSIS    [Toc]    [Back]

       diff [options] from-file to-file

DESCRIPTION    [Toc]    [Back]

       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 compares 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  compares	corresponding
 files in both directories, in alphabetical 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    [Toc]    [Back]
       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 letter 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	      is combined with -c or -u.  This option is obsolete.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
	      operation, 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 differing lines
	      from both files in if-then-else format.	For  more  details  on
	      what  can  be  specified	in the format string, consult the info
	      documentation of diff .

       -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	subdirectories
	      whose basenames match pattern.

       --exclude-from=file
	      When  comparing  directories,  ignore  files  and subdirectories
	      whose basenames match any pattern contained 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 suffix.

       -i     Ignore  changes  in case; consider upper- and lower-case letters
	      equivalent.

       -I regexp
	      Ignore changes that just insert or delete lines that match  reg-
	      exp.

       --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 reg-
	      exp.

       --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.

       -o     Use the old traditional output 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.

       --rcs  Output RCS-format diffs; like -f except that each command specifies
 the number of lines affected.

       -r
       --recursive
	      When  comparing directories, recursively compare any subdirectories
 found.

       -s
       --report-identical-files
	      Report when two files are the same.

       -S file
	      When comparing directories, start with the file file.   This  is
	      used for resuming an aborted comparison.

       --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 comparison.

       --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 horizontal white space when comparing lines.

       -W columns
       --width=columns
	      Use an output width of columns in side by side format.

       -x pattern
	      When comparing  directories,  ignore  files  and	subdirectories
	      whose basenames match pattern.

       -X file
	      When  comparing  directories,  ignore  files  and subdirectories
	      whose basenames match any pattern contained in file.

       -y     Use the side by side output format.

ENVIRONMENT    [Toc]    [Back]

       The environment variable DIFF_OPTIONS can hold a set of default options
       for  diff.   These options are interpreted first and can be overwritten
       by explicit command line parameters.

EXAMPLES    [Toc]    [Back]

       To save to a file some changes that you have made to your local	source
       tree  (possibly	including  new files), which you would like to show to
       others (perhaps using the send-pr(1) program), you could type

       diff -crN foo.orig foo >foo.diff

       where foo.orig and foo might be directory hierarchies or single	files.

SEE ALSO    [Toc]    [Back]

      
      
       cmp(1), comm(1), diff3(1), ed(1), patch(1), pr(1), sdiff(1).

DIAGNOSTICS    [Toc]    [Back]

       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)
[ Back ]
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