NAME

       diff - differential file comparator

SYNOPSIS

       diff [ -acefmnbwr ] file1 ... file2

DESCRIPTION

       Diff  tells  what  lines  must  be  changed  in two files to bring them into agreement.  If one file is a
       directory, then a file in that directory with basename the same as that of the other file  is  used.   If
       both  files  are  directories, similarly named files in the two directories are compared by the method of
       diff for text files and cmp(1) otherwise.  If more than two file names are given, then each  argument  is
       compared  to  the  last  argument  as  above.   The  -r  option  causes  diff  to process similarly named
       subdirectories recursively.  When processing more than one file, diff prefixes file  differences  with  a
       single line listing the two differing files, in the form of a diff command line.  The -m flag causes this
       behavior even when processing single files.

       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 -w option causes all white-space to be removed from input lines before  applying  the
       difference algorithm.

       The  -n  option  prefixes each range with file: and inserts a space around the a, c, and d verbs.  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. It may, however, be
       useful as input to a stream-oriented post-processor.

       The -c option includes three lines of context around each change, merging changes whose contexts overlap.
       The -a flag displays the entire file as context.

       Except in rare circumstances, diff finds a smallest sufficient set of file differences.

FILES

       /tmp/diff[12]

SOURCE

       /src/cmd/diff

SEE ALSO

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

DIAGNOSTICS

       Exit status is the empty string for no differences, for some, and for trouble.

BUGS

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

       When running diff on directories, the notion of what is a text file is open to debate.

                                                                                                    DIFF(1plan9)