DIFF3(1)                   OpenBSD Reference Manual                   DIFF3(1)

NAME
     diff3 - 3-way differential file comparison

SYNOPSIS
     diff3 [-3aEeXx] file1 file2 file3

DESCRIPTION
     The diff3 utility compares the contents of three different versions of a
     file, file1, file2 and file3, writing the result to the standard output.
     The options describe different methods of merging and purging the sepa-
     rate versions into a new file.  diff3 is used by rcs(1) to merge specific
     versions or create new versions.

     The options are as follows:

     -3      Produces an output script suitable for ed(1) with changes specif-
             ic only to file3.

     -a      Treat all files as ASCII.

     -E, -X  Similar to -e and -x, respectively, but treat overlapping changes
             (i.e., changes that would be noted with ==== in the normal list-
             ing) differently.  The overlapping lines from both files will be
             inserted by the edit script, bracketed by "<<<<<<" and ">>>>>>"
             lines.

     -e      Produces output in a form suitable as an input script for the
             ed(1) utility.  The script may then be used to merge differences
             common between all three files and differences specific to file1
             and file3.  In other words, the -e option ignores differences
             specific to file1 and file2, and those specific to file2 and
             file3.  It is useful for backing out changes specific to file2
             only.

     -x      Produces an output script suitable for ed(1) with changes specif-
             ic only to all three versions.

     The -E option is used by RCS merge(1) to ensure that overlapping changes
     in the merged files are preserved and brought to someone's attention.

     For example, suppose lines 7-8 are changed in both file1 and file2.  Ap-
     plying the edit script generated by the command

           $ diff3 -E file1 file2 file3

     to file1 results in the file:

           lines 1-6
           of file1
           <<<<<<< file1
           lines 7-8
           of file1
           =======
           lines 7-8
           of file3
           >>>>>>> file3
           rest of file1

     The default output of diff3 makes notation of the differences between all
     files, and those differences specific to each pair of files.  The changes
     are described by the commands necessary for ed(1) to create the desired
     target from the different versions.  See diff(1) for a description of the
     commands.

     ====   The lines beneath this notation are ranges of lines which are dif-
            ferent between all files.

     ====n  The lines beneath this notation are ranges of lines which are ex-
            clusively different in file n.

ENVIRONMENT
     TMPDIR  If the environment variable TMPDIR exists, diff3 will use the di-
             rectory specified by TMPDIR as the temporary directory.

FILES
     /tmp/d3a.XXXXXXXXXX     temporary file
     /tmp/d3b.XXXXXXXXXX     temporary file
     /usr/libexec/diff3prog  the actual executable

SEE ALSO
     diff(1), ed(1), merge(1), rcs(1), sdiff(1)

HISTORY
     A diff3 command appeared in Version 7 AT&T UNIX.

BUGS
     The -e option cannot catch and change lines which have `.' as the first
     and only character on the line.  The resulting script will fail on that
     line as `.' is an ed(1) editing command.

OpenBSD 4.7                      May 31, 2007                                2
