DIFF(1)              INTERACTIVE UNIX System              DIFF(1)



          NAME
               diff - differential file comparator

          SYNOPSIS
               diff [ -efbh ] file1 file2

          DESCRIPTION
               The diff command 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 direc-
               tory, then a file in that directory with the name 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 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 abbrevi-
               ated 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
               program may help maintain multiple versions of a file.  Only
               an ancestral file ($1) and a chain of version-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 suffi-
               cient 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 unlimited length.  Options -e and -f are
               unavailable with -h.

          FILES
               /tmp/d?????


          Rev. Base System                                           Page 1

          DIFF(1)              INTERACTIVE UNIX System              DIFF(1)



               /usr/lib/diffh for -h

          SEE ALSO
               bdiff(1), cmp(1), comm(1), ed(1).

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

          BUGS
               Editing scripts produced under the -e or -f option are naive
               about creating lines consisting of a single period (.).

          WARNINGS
               Missing newline at end of file X
               indicates that the last line of file X did not have a new-
               line.  If the lines are different, they will be flagged and
               output although the output will seem to indicate they are
               the same.




































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