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Unix Version 7 - man page for diff (v7 section 1)

DIFF(1) 			     General Commands Manual				  DIFF(1)

       diff - differential file comparator

       diff [ -efbh ] file1 file2

       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  let-
       ters  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 main-
       tain 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.

       /usr/lib/diffh for -h

       cmp(1), comm(1), ed(1)

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

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


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