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 spe-
       cial 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 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 com-
       pares the actual contents of a directory as if it were a
       file.  The file that is fully specified may not be stan-
       dard 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
       letter options (unless they take  an  argument)  can  be
       combined into a single command line word: -ac is equiva-
       lent 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              with  -c  or  -u.   This option is obsolete.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 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  (some-
              times much slower).

       -D name
              Make  merged  if-then-else  format output, condi-
              tional on the preprocessor macro name.

       -e
       --ed   Make output that is a valid ed script.

       --exclude=pattern
              When comparing directories, ignore files and sub-
              directories whose basenames match pattern.

       --exclude-from=file
              When comparing directories, ignore files and sub-
              directories 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 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 (some-
              times 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  com-
              parison.

       --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 com-
              parison.

       --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
              format.

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

       -X file
              When comparing directories, ignore files and sub-
              directories 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 differences were found, and 2 means trouble.



GNU Tools                  1993-09-22                   DIFF(1)
