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 stan-
       dard  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  corre-
       sponding files in both directories, in alphabetical order; this compar-
       ison 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 remain-
       ing 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 pre-
       ceded by -, and the other of which is a long name preceded by --.  Mul-
       tiple  single letter options (unless they take an argument) can be com-
       bined 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              is combined with -c or -u.  This option is obsolete.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  opera-
              tion, 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.

       -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 pre-
              processor 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 com-
              patibility.

       -H     Use heuristics to speed handling of large files that have numer-
              ous 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 pre-
              processor 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 speci-
              fies the number of lines affected.

       -N
       --new-file
              In directory comparison, if a file is found in only  one  direc-
              tory, 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  subdirecto-
              ries found.

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

       --recursive
              When comparing directories, recursively compare any  subdirecto-
              ries 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 comparison.

       --from-file=file
              Compare file to all operands.  file can be a directory.

       --to-file=file
              Compare all operands to file. file can be a directory.

       --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 numer-
              ous 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  opera-
              tion, 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 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.


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 dif-
       ferences were found, and 2 means trouble.



GNU Tools                          22sep1993                           DIFF(1)

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