DIFF(C)                  XENIX System V                   DIFF(C)



     Name
          diff - Compares two text files.

     Syntax
          diff [ -efbh ] file1 file2

     Description
          diff tells what lines must be changed in two files to bring
          them into agreement.  If file1 or file2 is a dash (-), the
          standard input is used.  If file1 or file2 is a directory,
          diff uses the file in that directory that has the same name
          as file (file2 or file1 respectively) it is compared to. For
          example:

               diff /tmp dog

          compares the file named dog, that is in the /tmp directory,
          with the file dog in the current directory.  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 -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
          procedure helps maintain multiple versions of a file:

               (shift; cat $*; echo '1,$p') | ed - $1

          This works by performing a set of editing operations on an
          original ancestral file.  This is done by combining the
          sequence of ed scripts given as all command line arguments
          except the first.  These scripts are presumed to have been
          created with diff in the order given on the command line.
          The set of editing operations is then piped as an editing



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     DIFF(C)                  XENIX System V                   DIFF(C)



          script to ed where all editing operations are performed on
          the ancestral file given as the first argument on the
          command line. The final version of the file is then printed
          on the standard output.  Only an ancestral file ($1) and a
          chain of version-to-version ed scripts ($2,$3,...) made by
          diff need be on hand.

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

          The -h option does a fast, less-rigorous job.  It works only
          when changed stretches are short and well separated, but
          also works on files of unlimited length.  The -e and -f
          cannot be used with the -h option.

     Files
          /tmp/d?????

          /usr/lib/diffh for -h

     See Also
          cmp(C), comm(C), ed(C)

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

     Notes
          Editing scripts produced under the -e or -f option do not
          always work correctly on lines consisting of a single period
          (.).
























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