509 lines
11 KiB
Groff
509 lines
11 KiB
Groff
.\" $FreeBSD$
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.TH DIFF 1 "22sep1993" "GNU Tools" "GNU Tools"
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.SH NAME
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diff \- find differences between two files
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.SH SYNOPSIS
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.B diff
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[options] from-file to-file
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.SH DESCRIPTION
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In the simplest case,
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.I diff
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compares the contents of the two files
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.I from-file
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and
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.IR to-file .
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A file name of
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.B \-
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stands for
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text read from the standard input. As a special case,
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.B "diff \- \-"
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compares a copy of standard input to itself.
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If
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.I from-file
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is a directory and
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.I to-file
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is not,
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.I diff
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compares the file in
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.I from-file
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whose file name is that of
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.IR to-file ,
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and vice versa. The non-directory file must not be
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.BR \- .
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If both
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.I from-file
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and
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.I to-file
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are directories,
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.I diff
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compares corresponding files in both directories, in
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alphabetical order; this comparison is not recursive unless the
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.B \-r
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or
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.B \-\-recursive
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option is given.
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.I diff
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never
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compares the actual contents of a directory as if it were a file. The
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file that is fully specified may not be standard input, because standard
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input is nameless and the notion of ``file with the same name'' does not
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apply.
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.B diff
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options begin with
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.BR \- ,
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so normally
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.I from-file
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and
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.I to-file
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may not begin with
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.BR \- .
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However,
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.B \-\-
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as an
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argument by itself treats the remaining arguments as file names even if
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they begin with
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.BR \- .
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.SS Options
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Below is a summary of all of the options that GNU
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.I diff
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accepts.
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Most options have two equivalent names, one of which is a single letter
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preceded by
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.BR \- ,
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and the other of which is a long name preceded by
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.BR \-\- .
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Multiple single letter options (unless they take an
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argument) can be combined into a single command line word:
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.B \-ac
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is
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equivalent to
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.BR "\-a \-c" .
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Long named options can be abbreviated to
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any unique prefix of their name. Brackets
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.RB ( [
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and
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.BR ] )
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indicate that an
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option takes an optional argument.
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.TP
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.BI \- lines
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Show
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.I lines
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(an integer) lines of context. This option does not
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specify an output format by itself; it has no effect unless it is
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combined with
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.B \-c
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or
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.BR \-u .
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This option is obsolete. For proper
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operation,
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.I patch
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typically needs at least two lines of context.
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.TP
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.B \-a
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Treat all files as text and compare them line-by-line, even if they
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do not seem to be text.
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.TP
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.B \-b
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Ignore changes in amount of white space.
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.TP
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.B \-B
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Ignore changes that just insert or delete blank lines.
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.TP
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.B \-\-brief
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Report only whether the files differ, not the details of the
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differences.
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.TP
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.B \-c
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Use the context output format.
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.TP
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.BI "\-C " lines
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.br
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.ns
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.TP
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.BI \-\-context[= lines ]
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Use the context output format, showing
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.I lines
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(an integer) lines of
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context, or three if
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.I lines
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is not given.
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For proper operation,
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.I patch
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typically needs at least two lines of
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context.
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.TP
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.BI \-\-changed\-group\-format= format
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Use
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.I format
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to output a line group containing differing lines from
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both files in if-then-else format.
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For more details on what can be specified in the
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.I format
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string, consult the info documentation of
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.I diff .
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.TP
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.B \-d
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Change the algorithm to perhaps find a smaller set of changes. This makes
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.I diff
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slower (sometimes much slower).
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.TP
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.BI "\-D " name
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Make merged if-then-else format output, conditional on the preprocessor
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macro
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.IR name .
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.TP
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.B \-e
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.br
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.ns
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.TP
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.B \-\-ed
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Make output that is a valid
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.I ed
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script.
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.TP
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.BI \-\-exclude= pattern
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When comparing directories, ignore files and subdirectories whose basenames
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match
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.IR pattern .
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.TP
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.BI \-\-exclude\-from= file
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When comparing directories, ignore files and subdirectories whose basenames
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match any pattern contained in
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.IR file .
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.TP
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.B \-\-expand\-tabs
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Expand tabs to spaces in the output, to preserve the alignment of tabs
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in the input files.
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.TP
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.B \-f
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Make output that looks vaguely like an
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.I ed
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script but has changes
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in the order they appear in the file.
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.TP
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.BI "\-F " regexp
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In context and unified format, for each hunk of differences, show some
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of the last preceding line that matches
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.IR regexp .
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.TP
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.B \-\-forward\-ed
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Make output that looks vaguely like an
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.B ed
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script but has changes
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in the order they appear in the file.
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.TP
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.B \-h
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This option currently has no effect; it is present for Unix
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compatibility.
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.TP
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.B \-H
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Use heuristics to speed handling of large files that have numerous
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scattered small changes.
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.TP
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.BI \-\-horizon\-lines= lines
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Do not discard the last
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.I lines
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lines of the common prefix
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and the first
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.I lines
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lines of the common suffix.
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.TP
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.B \-i
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Ignore changes in case; consider upper- and lower-case letters
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equivalent.
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.TP
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.BI "\-I " regexp
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Ignore changes that just insert or delete lines that match
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.IR regexp .
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.TP
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.BI \-\-ifdef= name
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Make merged if-then-else format output, conditional on the preprocessor
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macro
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.IR name .
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.TP
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.B \-\-ignore\-all\-space
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Ignore white space when comparing lines.
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.TP
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.B \-\-ignore\-blank\-lines
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Ignore changes that just insert or delete blank lines.
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.TP
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.B \-\-ignore\-case
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Ignore changes in case; consider upper- and lower-case to be the same.
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.TP
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.BI \-\-ignore\-matching\-lines= regexp
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Ignore changes that just insert or delete lines that match
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.IR regexp .
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.TP
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.B \-\-ignore\-space\-change
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Ignore changes in amount of white space.
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.TP
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.B \-\-initial\-tab
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Output a tab rather than a space before the text of a line in normal or
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context format. This causes the alignment of tabs in the line to look
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normal.
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.TP
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.B \-l
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Pass the output through
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.I pr
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to paginate it.
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.TP
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.BI "\-L " label
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.br
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.ns
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.TP
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.BI \-\-label= label
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Use
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.I label
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instead of the file name in the context format
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and unified format
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headers.
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.TP
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.B \-\-left\-column
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Print only the left column of two common lines in side by side format.
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.TP
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.BI \-\-line\-format= format
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Use
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.I format
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to output all input lines in in-then-else format.
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.TP
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.B \-\-minimal
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Change the algorithm to perhaps find a smaller set of changes. This
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makes
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.I diff
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slower (sometimes much slower).
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.TP
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.B \-n
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Output RCS-format diffs; like
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.B \-f
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except that each command
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specifies the number of lines affected.
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.TP
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.B \-N
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.br
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.ns
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.TP
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.B \-\-new\-file
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In directory comparison, if a file is found in only one directory,
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treat it as present but empty in the other directory.
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.TP
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.BI \-\-new\-group\-format= format
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Use
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.I format
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to output a group of lines taken from just the second
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file in if-then-else format.
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.TP
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.BI \-\-new\-line\-format= format
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Use
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.I format
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to output a line taken from just the second file in
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if-then-else format.
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.TP
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.B \-o
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Use the old traditional output format.
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.TP
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.BI \-\-old\-group\-format= format
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Use
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.I format
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to output a group of lines taken from just the first
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file in if-then-else format.
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.TP
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.BI \-\-old\-line\-format= format
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Use
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.I format
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to output a line taken from just the first file in
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if-then-else format.
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.TP
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.B \-p
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Show which C function each change is in.
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.TP
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.B \-P
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When comparing directories, if a file appears only in the second
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directory of the two, treat it as present but empty in the other.
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.TP
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.B \-\-paginate
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Pass the output through
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.I pr
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to paginate it.
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.TP
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.B \-q
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Report only whether the files differ, not the details of the
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differences.
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.TP
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.B \-\-rcs
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Output RCS-format diffs; like
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.B \-f
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except that each command
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specifies the number of lines affected.
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.TP
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.B \-r
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.br
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.ns
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.TP
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.B \-\-recursive
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When comparing directories, recursively compare any subdirectories
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found.
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.TP
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.B \-s
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.br
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.ns
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.TP
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.B \-\-report\-identical\-files
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Report when two files are the same.
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.TP
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.BI "\-S " file
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When comparing directories, start with the file
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.IR file .
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This is
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used for resuming an aborted comparison.
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.TP
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.B \-\-sdiff\-merge\-assist
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Print extra information to help
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.IR sdiff .
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.I sdiff
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uses this
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option when it runs
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.IR diff .
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This option is not intended for users
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to use directly.
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.TP
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.B \-\-show\-c\-function
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Show which C function each change is in.
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.TP
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.BI \-\-show\-function\-line= regexp
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In context and unified format, for each hunk of differences, show some
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of the last preceding line that matches
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.IR regexp .
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.TP
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.B \-\-side\-by\-side
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Use the side by side output format.
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.TP
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.B \-\-speed\-large\-files
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Use heuristics to speed handling of large files that have numerous
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scattered small changes.
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.TP
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.BI \-\-starting\-file= file
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When comparing directories, start with the file
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.IR file .
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This is
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used for resuming an aborted comparison.
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.TP
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.B \-\-suppress\-common\-lines
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Do not print common lines in side by side format.
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.TP
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.B \-t
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Expand tabs to spaces in the output, to preserve the alignment of tabs
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in the input files.
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.TP
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.B \-T
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Output a tab rather than a space before the text of a line in normal or
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context format. This causes the alignment of tabs in the line to look
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normal.
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.TP
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.B \-\-text
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Treat all files as text and compare them line-by-line, even if they
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do not appear to be text.
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.TP
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.B \-u
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Use the unified output format.
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.TP
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.BI \-\-unchanged\-group\-format= format
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Use
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.I format
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to output a group of common lines taken from both files
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in if-then-else format.
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.TP
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.BI \-\-unchanged\-line\-format= format
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Use
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.I format
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to output a line common to both files in if-then-else
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format.
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.TP
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.B \-\-unidirectional\-new\-file
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When comparing directories, if a file appears only in the second
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directory of the two, treat it as present but empty in the other.
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.TP
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.BI "\-U " lines
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.br
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.ns
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.TP
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.BI \-\-unified[= lines ]
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Use the unified output format, showing
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.I lines
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(an integer) lines of
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context, or three if
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.I lines
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is not given.
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For proper operation,
|
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.I patch
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typically needs at least two lines of
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context.
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.TP
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.B \-v
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.br
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.ns
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.TP
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.B \-\-version
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Output the version number of
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.IR diff .
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.TP
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.B \-w
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Ignore horizontal white space when comparing lines.
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.TP
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.BI "\-W " columns
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.br
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.ns
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.TP
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.BI \-\-width= columns
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Use an output width of
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.I columns
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in side by side format.
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.TP
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.BI "\-x " pattern
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When comparing directories, ignore files and subdirectories whose basenames
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match
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.IR pattern .
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.TP
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.BI "\-X " file
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When comparing directories, ignore files and subdirectories whose basenames
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match any pattern contained in
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.IR file .
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.TP
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.B \-y
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Use the side by side output format.
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.SH RETURN VALUE
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.I diff
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returns 0 if the files are identical or 1 if the files differ.
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If one or both of the files cannot be opened,
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then the return value is set to 2.
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.SH ENVIRONMENT
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The environment variable
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.B DIFF_OPTIONS
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can hold a set of default
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options for
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.I diff.
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These options are interpreted first and can be overwritten by explicit command
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line parameters.
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.SH EXAMPLES
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To save to a file some changes that you have made to your local source
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tree (possibly including new files), which you would like to show to others
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(perhaps using the
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.B send-pr(1)
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program), you could type
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.sp
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diff -crN foo.orig foo >foo.diff
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.sp
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where
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.I foo.orig
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and
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.I foo
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might be directory hierarchies or single files.
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.SH SEE ALSO
|
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cmp(1), comm(1), diff3(1), ed(1), patch(1), pr(1), sdiff(1).
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.SH DIAGNOSTICS
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An exit status of 0 means no differences were found, 1 means some
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differences were found, and 2 means trouble.
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