diff

DIFF(1plan9)                                                        DIFF(1plan9)



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)