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DIFF(1)								       DIFF(1)

NAME    [Toc]    [Back]

     diff - differential file and directory comparator

SYNOPSIS    [Toc]    [Back]

     diff [-lrs] [-Sname] [-cefhn] [-xpat] [-biwt] dir1	dir2
     diff [-cefhn] [-biwt] file1 file2
     diff [-Dstring] [-biw] file1 file2
     GNU diff options:
     diff [-#] [-aBdHNpqTuv] [-Cnum] [-Fexp] [-Iexp] [-Llab]

DESCRIPTION    [Toc]    [Back]

     If	both arguments are directories,	diff sorts the contents	of the
     directories by name, and then runs	the regular file diff algorithm
     (described	below) on text files which are different.  Binary files	which
     differ (unless -a is specified), common subdirectories, and files which
     appear in only one	directory are listed.  Options when comparing
     directories are:

     -l	  long output format; each text	file diff is piped through pr(1) to
	  paginate it, other differences are remembered	and summarized after
	  all text file	differences are	reported.

     -r	  causes application of	diff recursively to common subdirectories

     -s	  causes diff to report	files which are	the same, which	are otherwise
	  not mentioned.

	  starts a directory diff in the middle	beginning with file name.

	  adds pat to a	list of	regular	expressions.  There can	be several
	  -xpat	options.  Any directory	or file	(base) name matching one of
	  the patterns is skipped.  The	special	characters available in	the
	  pattern pat are similar to those used	in egrep(1).  For example, the
	  following command will ignore	all "hidden" files and all RCS

		   diff	-r '-x^\.' '-x,v$' foo bar

     When run on regular files,	and when comparing text	files which differ
     during directory comparison, diff tells what lines	must be	changed	in the
     files to bring them into agreement.  Except in rare circumstances,	diff
     finds a smallest sufficient set of	file differences.  If neither file1
     nor file2 is a directory, then either may be given	as `-',	in which case
     the standard input	is used.  If file1 is a	directory, then	a file in that
     directory whose file-name is the same as the file-name of file2 is	used
     (and vice versa).	If both	file1 and file2	are directories, then files
     (or files and directories with -r)	with identical names are compared.

									Page 1

DIFF(1)								       DIFF(1)

     There are several options for output format; the default output format
     contains lines of these forms:

	  n1 a n3,n4
	  n1,n2	d n3
	  n1,n2	c n3,n4

     These lines resemble ed commands to convert file1 into file2.  The
     numbers after the letters pertain to file2.  In fact, by exchanging `a'
     for `d' and reading backward one may ascertain equally how	to convert
     file2 into	file1.	As in ed, identical pairs where	n1 = n2	or n3 =	n4 are
     abbreviated as a single number.

     Following each of these lines come	all the	lines that are affected	in the
     first file	flagged	by `<',	then all the lines that	are affected in	the
     second file flagged by `>'.

     Except for	-b, -w,	-i or -t which may be given with any of	the others,
     the following options are mutually	exclusive:

     -e	      produces a script	of a, c	and d commands for the editor ed,
	      which will recreate file2	from file1.  In	connection with	-e,
	      the following shell program may help maintain multiple versions
	      of a file.  Only an ancestral file ($1) and a chain of versionto-version
 ed scripts ($2,$3,...)	made by	diff need be on	hand.
	      A	`latest	version' appears on the	standard output.

		      (shift; cat $*; echo '1,$p') | ed	- $1

	      Extra commands are added to the output when comparing
	      directories with -e, so that the result is a sh(1) script	for
	      converting text files which are common to	the two	directories
	      from their state in dir1 to their	state in dir2.

     -f	      produces a script	similar	to that	of -e, not useful with ed, and
	      in the opposite order.

     -n	      produces a script	similar	to that	of -e, but in the opposite
	      order and	with a count of	changed	lines on each insert or	delete
	      command.	This is	the form used by the RCS commands for storing
	      a	revision change.

     -c	      produces a diff with 3 lines of context.	Use the	-Cnum option
	      to specify the number of lines.  With -c the output format is
	      modified slightly:  the output beginning with identification of
	      the files	involved and their creation dates and then each	change
	      is separated by a	line with a dozen *'s.	The lines removed from
	      file1 are	marked with `- '; those	added to file2 are marked `+
	      '.  Lines	which are changed from one file	to the other are
	      marked in	both files with	`! '.

	      Changes which lie	within <context> lines of each other are

									Page 2

DIFF(1)								       DIFF(1)

	      grouped together on output.

     -h	      has no affect. It	is present for compatibility with odiff(1).

     -Dstring causes diff to create a merged version of	file1 and file2	on the
	      standard output, with C preprocessor controls included so	that a
	      compilation of the result	without	defining string	is equivalent
	      to compiling file1, while	defining string	will yield file2.

     -b	      causes trailing blanks (spaces and tabs) to be ignored, and
	      other strings of blanks to compare equal.

     -w	      is similar to -b but causes whitespace (blanks and tabs) to be
	      totally ignored.	E.g., ``if ( a == b )''	will compare equal to

     -i	      ignores the case of letters.  E.g., ``A''	will compare equal to

     -t	      will expand tabs in output lines.	 Normal	or -c output adds
	      character(s) to the front	of each	line which may foul up the
	      indentation of the original source lines and make	the output
	      listing difficult	to interpret.  This option will	preserve the
	      original source's	indentation.

GNU DIFF OPTIONS    [Toc]    [Back]

     -#	      Show # lines (an integer)	of context.  This option does not
	      specify an output	format by itself; it has no effect unless it
	      is combined with -c or -u.

     -a	      Treat all	files as text and compare them line-by-line, even if
	      they do not appear to be text

     -B	      Ignore changes that just insert or delete	blank lines.

     -Cnum    Use the context output format, showing lines (an integer)	lines
	      of context

     -d	      Change the algorithm to find a guaranteed	minimal	set of
	      changes.	This makes diff	slower (sometimes much slower).

     -Fexp    In context and unified format, for each hunk of differences,
	      show some	of the last preceding line that	matches	exp.

     -H	      Use heuristics to	speed handling of large	files that have
	      numerous scattered small changes

     -Iexp    Ignore changes that just insert or delete	lines that match exp.

     -Llab    Use lab instead of the pathname in the context format and
	      unified format headers

									Page 3

DIFF(1)								       DIFF(1)

     -N	      In directory comparison, if a file is found in only one
	      directory, treat it as present but empty in the other directory.

     -p	      Show which C function each change	is in.

     -q	      Report only whether the files differ, not	the details of the

     -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.

     -u	      Use the unified output format

     -v	      Display the version string.

FILES    [Toc]    [Back]

     /usr/bin/odiff    executable for odiff.
     /bin/diff	       executable for GNU derived diff.
     /bin/pr	       executed	by the -l option.

SEE ALSO    [Toc]    [Back]

     bdiff(1), cc(1), cmp(1), comm(1), odiff(1), diff3(1), ed(1),

DIAGNOSTICS    [Toc]    [Back]

     Exit status is 0 for no differences, 1 for	some differences, 2 for

PERFORMANCE    [Toc]    [Back]

     The GNU derived diff and older BSD	derived	odiff use different
     algorithms.  If the two files to be compared fit in main memory, then
     diff is faster, but if they don't fit, diff can cause severe paging.  The
     odiff algorithm uses a small, fixed amount	of memory even on large	files.
     The multiple pass algorithm of odiff is up	to two or three	times slower
     than diff,	on files that fit in memory, but can be	many times faster on
     files that	don't fit.

     The diff command automatically invokes the	odiff (searching for odiff
     along $PATH) on files that	have a combined	size larger than one-fourth of
     memory size, if no	GNU specific diff options were specified.  If that
     fails, then diff silently does the	work itself.

     You can force either variant: specifying -H always	gets diff, specifying
     odiff always gets odiff.

									PPPPaaaaggggeeee 4444
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