term% ls -F
term% pwd
term% cat index.txt
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 num‐
       bers 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  connec‐
       tion  with  -e,  the following shell program may help maintain multiple
       versions of a file.  Only an ancestral file ($1) and a  chain  of  ver‐
       sion-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  un‐
       limited 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 cre‐
       ating lines consisting of a single `.'.