NAME
	  diff - Compares text files

     SYNOPSIS
	  diff [-c | -C	number | -e | -f | -h |	-n] [-bilrstw] [-
	  Sfile] directory1 directory2

	  diff [-c | -C	number | -e | -f | -h |	-n] [-bitw] file1
	  file2

	  diff [-Dstring] [-bitw] file1	file2


     FLAGS
	  The -c, -C, -e, -f, -h, and -n flags are mutually exclusive.

	  The -r, -s, and -S flags can be specified with directory
	  comparisons only.

	  The -b, -i, -l, -t, and -w flags can be used in combination
	  with any others and in both file and directory comparisons.


	  -b  Causes trailing spaces and tabs (blanks) to be ignored,
	      and other	strings	of spaces and tabs to be considered
	      identical	by diff.

	  -c  Produces a listing with the default number of lines of
	      context (3 lines).  The output lists the files being
	      compared and their last modification dates, then lists
	      the differing lines.  Lines that are changed from	one
	      file to the other	are marked in both files with an !
	      (exclamation point).  Changes that lie within the	speci-
	      fied number of lines of each other are grouped together
	      on output.

	  -C number
	      Produces output that provides number lines of context
	      (where number is a positive decimal integer).

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

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

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



	      Extra commands are added to the output when comparing
	      directories with -e; the result is a sh script for con-
	      verting text files common	to the directories from	their
	      state in directory1 to their state in directory2.

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

	  -h  Performs a faster	comparison.  This flag only works when
	      the changed sections are short and well separated, but
	      it does work on files of any length.  The	-e and -f
	      flags are	not available when you use the -h flag.

	  -i  Ignores the case of letters.  For	example, A is con-
	      sidered identical	to a.

	  -l  Specifies	long output format; each text file diff	list-
	      ing is piped through pr to paginate it, other differ-
	      ences are	remembered and summarized after	all text file
	      differences are reported.	 (Directory comparisons	only.)

	  -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
	      revision control system (RCS).

	  -r  Checks files in common subdirectories recursively.

	  -s  Reports files that are the same, which are otherwise not
	      mentioned.

	  -Sfile
	      Starts a directory diff in the middle, beginning with
	      file.  (Directory	comparisons only.)

	  -t  Expands tabs in output lines.  Normal or -c output adds
	      characters to the	front of each line that	can affect the
	      indentation of the original source lines and make	the
	      output listing difficult to interpret.  This flag
	      preserves	the original source's indentation.

	  -w  Is similar to -b,	but causes whitespace (spaces and
	      tabs) to be ignored.  For	example, if ( a	== b ) is con-
	      sidered identical	to if(a==b).

     DESCRIPTION
	Input Options
	  If neither file1 nor file2 is	a directory, then either can
	  be given as -	(dash),	in which case the standard input is
	  used.	 If file1 is a directory and file2 is a	file, or vice
	  versa, a file	in the specified directory with	the same name
	  as the specified file	is used.

	  If both arguments are	directories, diff sorts	the contents
	  of the directories by	name, and then runs the	regular	diff
	  file algorithm on text files that are	different.  Binary
	  files	that differ, common subdirectories, and	files that
	  appear in only one directory are also	listed.

	Output Options
	  There	are several choices for	output format.	The default
	  output format	contains lines of these	forms:

	  number1 a number2,number3
	  number1,number2 d number3
	  number1,number2 c number3,number4



	  These	lines resemble ed commands to convert file1 into
	  file2.  a indicates that a line or lines were	added to one
	  of the files;	d indicates that a line	or lines were deleted;
	  and c	indicates that a line or lines were changed.  The
	  numbers after	the letters pertain to file2.  In fact,	by
	  exchanging a for d and reading backward one can ascertain
	  equally how to convert file2 into file1.  As in ed, identi-
	  cal pairs where number1 = number2 or number3 = number4 are
	  abbreviated as a single number.

	  Following each of these lines	come all the lines that	are
	  affected in the first	file, flagged by < (left angle
	  bracket), then all the lines that are	affected in the	second
	  file,	flagged	by > (right angle bracket).

	  Except in rare circumstances,	diff finds the smallest	suffi-
	  cient	set of file differences.

     EXAMPLES
	   1.  To compare two files, enter:

	       diff chap1.bak chap1



	       This displays the differences between the files
	       chap1.bak and chap1.

	   2.  To compare two files, ignoring differences in the
	       amount of white space, enter:

	       diff -b prog.c.bak prog.c



	       If two lines differ only	in the number of spaces	and
	       tabs between words, then	the diff command considers
	       them to be the same.

	   3.  To create a file	containing commands that the ed	com-
	       mand can	use to reconstruct one file from another,
	       enter:

	       diff -e ch2 ch2.old > new.old.ed



	       This creates a file named new.to.old.ed that contains
	       the ed subcommands to change chap2 back into the	ver-
	       sion of the text	found in chap2.old.  In	most cases,
	       new.to.old.ed is	a much smaller file than chap2.old.

	   4.  You can save disk space by deleting chap2.old, and you
	       can reconstruct it at any time by entering:

	       (cat new.old.ed ; echo '1,$p') |	ed - ch2 > ch2.old



	       The commands in parentheses add 1,$p to the end of the
	       editing commands	sent to	the ed editor.	The 1,$p
	       causes the ed command to	write the file to standard
	       output after editing it.	 This modified command
	       sequence	is then	piped to the ed	command	( | ed ), and
	       the editor reads	it as standard input.  The - flag
	       causes the ed command not to display the	file size and
	       other extra information,	since it would be mixed	with
	       the text	of chap2.old.


     FILES
	  /usr/lbin/diffh
		     For the -h	flag.

	  /usr/bin/pr
		     For the -l	flag.


     NOTES
	   1.  Editing scripts produced	by the -e or -f	flags cannot
	       create lines consisting of a single . (dot) character.

	   2.  Block, character, or FIFO special files cannot be used
	       with diff because they cause the	command	to exit.


     EXIT VALUES
	  An exit value	of 0 (zero) indicates no differences, 1	indi-
	  cates	differences found, and a number	greater	than 1 indi-
	  cates	an error.

     RELATED INFORMATION
	  Commands:  bdiff(1), cmp(1), comm(1),	diff3(1),
	  ed(1)/red(1).