1DIFF(1)                     General Commands Manual                    DIFF(1)
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NAME

6       diff - differential file comparator
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SYNOPSIS

9       diff [ -efbh ] file1 file2
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DESCRIPTION

12       Diff  tells  what lines must be changed in two files to bring them into
13       agreement.  If file1 (file2) is `-', the standard input  is  used.   If
14       file1 (file2) is a directory, then a file in that directory whose file-
15       name is the same as the file-name of file2 (file1) is used.  The normal
16       output contains lines of these forms:
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18            n1 a n3,n4
19            n1,n2 d n3
20            n1,n2 c n3,n4
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22       These lines resemble ed commands to convert file1 into file2.  The num‐
23       bers after the letters pertain to file2.  In fact,  by  exchanging  `a'
24       for  `d'  and reading backward one may ascertain equally how to convert
25       file2 into file1.  As in ed, identical pairs where n1 = n2 or n3  =  n4
26       are abbreviated as a single number.
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28       Following  each  of these lines come all the lines that are affected in
29       the first file flagged by `<', then all the lines that are affected  in
30       the second file flagged by `>'.
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32       The  -b  option  causes trailing blanks (spaces and tabs) to be ignored
33       and other strings of blanks to compare equal.
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35       The -e option produces a script of a, c and d commands for  the  editor
36       ed,  which  will  recreate  file2 from file1.  The -f option produces a
37       similar script, not useful with ed, in the opposite order.  In  connec‐
38       tion  with  -e,  the following shell program may help maintain multiple
39       versions of a file.  Only an ancestral file ($1) and a  chain  of  ver‐
40       sion-to-version ed scripts ($2,$3,...) made by diff need be on hand.  A
41       `latest version' appears on the standard output.
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43            (shift; cat $*; echo ´1,$p´) ⎪ ed - $1
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45       Except in rare circumstances, diff finds a smallest sufficient  set  of
46       file differences.
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48       Option  -h  does  a fast, half-hearted job.  It works only when changed
49       stretches are short and well separated,  but  does  work  on  files  of
50       unlimited length.  Options -e and -f are unavailable with -h.
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FILES

53       /tmp/d?????
54       /usr/lib/diffh for -h
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SEE ALSO

57       cmp(1), comm(1), ed(1)
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DIAGNOSTICS

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

63       Editing scripts produced under the -e or -f option are naive about cre‐
64       ating lines consisting of a single `.'.
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