diff

File: diff.info,  Node: Invoking diff,  Next: Invoking diff3,  Prev: Invoking cmp,  Up: Top

Invoking `diff'
***************

   The format for running the `diff' command is:

     diff OPTIONS... FILES...

   In the simplest case, two file names FROM-FILE and TO-FILE are
given, and `diff' compares the contents of 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 one file is a directory and the other is not, `diff' compares the
file in the directory whose name is that of the non-directory.  The
non-directory file must not be `-'.

   If two file names are given and both 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.

   If the `--from-file=FILE' option is given, the number of file names
is arbitrary, and FILE is compared to each named file.  Similarly, if
the `--to-file=FILE' option is given, each named file is compared to
FILE.

   `diff' options begin with `-', so normally file names may not begin
with `-'.  However, `--' as an argument by itself treats the remaining
arguments as file names even if they begin with `-'.

   An exit status of 0 means no differences were found, 1 means some
differences were found, and 2 means trouble.

* Menu:

* diff Options:: Summary of options to `diff'.

File: diff.info,  Node: diff Options,  Up: Invoking diff

Options to `diff'
=================

   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.

`-a'
`--text'
     Treat all files as text and compare them line-by-line, even if they
     do not seem to be text.  *Note Binary::.

`-b'
`--ignore-space-change'
     Ignore changes in amount of white space.  *Note White Space::.

`-B'
`--ignore-blank-lines'
     Ignore changes that just insert or delete blank lines.  *Note
     Blank Lines::.

`--binary'
     Read and write data in binary mode.  *Note Binary::.

`-c'
     Use the context output format, showing three lines of context.
     *Note Context Format::.

`-C LINES'
`--context[=LINES]'
     Use the context output format, showing LINES (an integer) lines of
     context, or three if LINES is not given.  *Note Context Format::.
     For proper operation, `patch' typically needs at least two lines of
     context.

     On older systems, `diff' supports an obsolete option `-LINES' that
     has effect when combined with `-c' or `-p'.  POSIX 1003.1-2001
     (*note Standards conformance::) does not allow this; use `-C LINES'
     instead.

`--changed-group-format=FORMAT'
     Use FORMAT to output a line group containing differing lines from
     both files in if-then-else format.  *Note Line Group Formats::.

`-d'
`--minimal'
     Change the algorithm perhaps find a smaller set of changes.  This
     makes `diff' slower (sometimes much slower).  *Note diff
     Performance::.

`-D NAME'
`--ifdef=NAME'
     Make merged `#ifdef' format output, conditional on the preprocessor
     macro NAME.  *Note If-then-else::.

`-e'
`--ed'
     Make output that is a valid `ed' script.  *Note ed Scripts::.

`-E'
`--ignore-tab-expansion'
     Ignore changes due to tab expansion.  *Note White Space::.

`-f'
`--forward-ed'
     Make output that looks vaguely like an `ed' script but has changes
     in the order they appear in the file.  *Note Forward ed::.

`-F REGEXP'
`--show-function-line=REGEXP'
     In context and unified format, for each hunk of differences, show
     some of the last preceding line that matches REGEXP.  *Note
     Specified Headings::.

`--from-file=FILE'
     Compare FILE to each operand; FILE may be a directory.

`--help'
     Output a summary of usage and then exit.

`--horizon-lines=LINES'
     Do not discard the last LINES lines of the common prefix and the
     first LINES lines of the common suffix.  *Note diff Performance::.

`-i'
`--ignore-case'
     Ignore changes in case; consider upper- and lower-case letters
     equivalent.  *Note Case Folding::.

`-I REGEXP'
`--ignore-matching-lines=REGEXP'
     Ignore changes that just insert or delete lines that match REGEXP.
     *Note Specified Folding::.

`--ignore-file-name-case'
     Ignore case when comparing file names during recursive comparison.
     *Note Comparing Directories::.

`-l'
`--paginate'
     Pass the output through `pr' to paginate it.  *Note Pagination::.

`--label=LABEL'
     Use LABEL instead of the file name in the context format (*note
     Context Format::) and unified format (*note Unified Format::)
     headers.  *Note RCS::.

`--left-column'
     Print only the left column of two common lines in side by side
     format.  *Note Side by Side Format::.

`--line-format=FORMAT'
     Use FORMAT to output all input lines in if-then-else format.
     *Note Line Formats::.

`-n'
`--rcs'
     Output RCS-format diffs; like `-f' except that each command
     specifies the number of lines affected.  *Note RCS::.

`-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.  *Note
     Comparing Directories::.

`--new-group-format=FORMAT'
     Use FORMAT to output a group of lines taken from just the second
     file in if-then-else format.  *Note Line Group Formats::.

`--new-line-format=FORMAT'
     Use FORMAT to output a line taken from just the second file in
     if-then-else format.  *Note Line Formats::.

`--old-group-format=FORMAT'
     Use FORMAT to output a group of lines taken from just the first
     file in if-then-else format.  *Note Line Group Formats::.

`--old-line-format=FORMAT'
     Use FORMAT to output a line taken from just the first file in
     if-then-else format.  *Note Line Formats::.

`-p'
`--show-c-function'
     Show which C function each change is in.  *Note C Function
     Headings::.

`-q'
`--brief'
     Report only whether the files differ, not the details of the
     differences.  *Note Brief::.

`-r'
`--recursive'
     When comparing directories, recursively compare any subdirectories
     found.  *Note Comparing Directories::.

`-s'
`--report-identical-files'
     Report when two files are the same.  *Note Comparing Directories::.

`-S FILE'
`--starting-file=FILE'
     When comparing directories, start with the file FILE.  This is
     used for resuming an aborted comparison.  *Note Comparing
     Directories::.

`--speed-large-files'
     Use heuristics to speed handling of large files that have numerous
     scattered small changes.  *Note diff Performance::.

`--strip-trailing-cr'
     Strip any trailing carriage return at the end of an input line.
     *Note Binary::.

`--suppress-common-lines'
     Do not print common lines in side by side format.  *Note Side by
     Side Format::.

`-t'
`--expand-tabs'
     Expand tabs to spaces in the output, to preserve the alignment of
     tabs in the input files.  *Note Tabs::.

`-T'
`--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.  *Note Tabs::.

`--to-file=FILE'
     Compare each operand to FILE; FILE may be a directory.

`-u'
     Use the unified output format, showing three lines of context.
     *Note Unified Format::.

`--unchanged-group-format=FORMAT'
     Use FORMAT to output a group of common lines taken from both files
     in if-then-else format.  *Note Line Group Formats::.

`--unchanged-line-format=FORMAT'
     Use FORMAT to output a line common to both files in if-then-else
     format.  *Note Line Formats::.

`--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.
     *Note Comparing Directories::.

`-U LINES'
`--unified[=LINES]'
     Use the unified output format, showing LINES (an integer) lines of
     context, or three if LINES is not given.  *Note Unified Format::.
     For proper operation, `patch' typically needs at least two lines of
     context.

     On older systems, `diff' supports an obsolete option `-LINES' that
     has effect when combined with `-u'.  POSIX 1003.1-2001 (*note
     Standards conformance::) does not allow this; use `-U LINES'
     instead.

`-v'
`--version'
     Output version information and then exit.

`-w'
`--ignore-all-space'
     Ignore white space when comparing lines.  *Note White Space::.

`-W COLUMNS'
`--width=COLUMNS'
     Output at most COLUMNS (default 130) print columns per line in
     side by side format.  *Note Side by Side Format::.

`-x PATTERN'
`--exclude=PATTERN'
     When comparing directories, ignore files and subdirectories whose
     basenames match PATTERN.  *Note Comparing Directories::.

`-X FILE'
`--exclude-from=FILE'
     When comparing directories, ignore files and subdirectories whose
     basenames match any pattern contained in FILE.  *Note Comparing
     Directories::.

`-y'
`--side-by-side'
     Use the side by side output format.  *Note Side by Side Format::.