DIFF(1) 						      General Commands Manual							   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 following 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 sufficient 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

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 `.'.

																	   DIFF(1)