DIFF(1)							  DIFF(1)

NAME
       diff - differential file comparator

SYNOPSIS
       diff [ -efbh ] file1 file2

DESCRIPTION
       Diff  tells  what  lines	 must  be changed in two files to
       bring them into agreement.  If file1 (file2) is	`-',  the
       standard	 input is used.	 If file1 (file2) is a directory,
       then a file in that directory whose file-name is the  same
       as  the	file-name  of  file2 (file1) is used.  The normal
       output 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 `>'.

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

       The -e option produces a script of a, c and d commands for
       the editor ed, which will recreate file2 from file1.   The
       -f  option  produces a similar script, not useful with ed,
       in the opposite order.  In connection with -e, the follow-
       ing shell program may 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 version' appears on the standard  output.

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

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

       Option -h does a fast, half-hearted job.	  It  works  only
       when  changed  stretches are short and well separated, but
       does work on files of unlimited length.	Options -e and -f
       are unavailable with -h.

FILES
       /tmp/d?????
       /usr/lib/diffh for -h

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DIFF(1)							  DIFF(1)

SEE ALSO
       cmp(1), comm(1), ed(1)

DIAGNOSTICS
       Exit  status  is	 0  for no differences, 1 for some, 2 for
       trouble.

BUGS
       Editing scripts produced under the -e  or  -f  option  are
       naive about creating lines consisting of a single `.'.

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