diff3(1)

NAME
     diff3 - 3-way differential file comparison

SYNOPSIS
     diff3 [ -exEX3 [-i | -m] [-L label1 -L label3] ] file1 file2 file3

DESCRIPTION
     Diff3 compares three versions of a file, and publishes disagreeing ranges
     of text flagged with these codes:

     ====            all three files differ

     ====1           file1 is different

     ====2           file2 is different

     ====3           file3 is different

     The type of change suffered in converting a given range of a given file
     to some other is indicated in one of these ways:

     f : n1 a        Text is to be appended after line number n1 in file f,
                     where f = 1, 2, or 3.

     f : n1 , n2 c   Text is to be changed in the range line n1 to line n2.
                     If n1 = n2, the range may be abbreviated to n1.

     The original contents of the range follows immediately after a c
     indication.  When the contents of two files are identical, the contents
     of the lower-numbered file is suppressed.

     The -m option produces a merge script on the output of diff3.  If none of
     -eExX3 is specified along with -m, then the format of option -E is
     presumed.  If the -m option is used, then binary files, files without
     trailing newline, and files with excessively long lines can be
     successfully merged.

     If no -m option is specified, then under the -e option, diff3 publishes a
     script for the editor ed(1) that will incorporate into file1 all changes
     between file2 and file3, i.e.  the changes that normally would be flagged
     ==== and ====3.  Option -x (-3) produces a script to incorporate only
     changes flagged ==== (====3).  The following command will apply the
     resulting script to `file1', and emit the result on the output stream.

                (cat script; echo '1,$p') | ed - file1

     The -E and -X are similar to -e and -x, respectively, but treat
     overlapping changes (i.e., changes that would be flagged with ==== in the
     normal listing) differently.  The overlapping lines from both files will
     be inserted by the edit script, bracketed by "<<<<<<" and ">>>>>>" lines.
     For example, suppose lines 7-8 are changed in both file1 and file3.  The
     merged output of the command

                           "diff3 -m file1 file2 file3"
     contains:

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

     If there are overlaps, the user should edit the result and delete one of
     the alternatives.  If the -L label1 and -L label3 options are given, the
     labels are output in place of the names file1 and file3 in overlap
     reports.

     If the option -i is specified along with one of the options -exEX3, then
     the resulting edit script has the editor commands

               w
               q

     added at the end.  Then the following command will update `file1' in
     place with the changes.

                ed - file1 < script

SEE ALSO
     diff(1), ed(1).

BUGS
     If merges are done by generating explicit scripts to input to the editor,
     rather than by using the -m option, the merge is limited by the
     capabilities of the editor ed(1).  The editor cannot handle excessively
     long lines, binary files (with nul bytes) or files without a trailing
     newline.

DIAGNOSTICS
     An exit status of 0 means diff3 was successful, 1 means some overlaps
     were found, and 2 means trouble.