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.Dd June 23, 2022 .Dt DIFF3 1 .Os .Sh NAME .Nm diff3 .Nd 3-way differential file comparison .Sh SYNOPSIS .Nm .Op Fl 3AaEeimTXx .Op Fl Fl diff-program Ar program .Op Fl Fl strip-trailing-cr .Op Fl L | Fl Fl label Ar label1 .Op Fl L | Fl Fl label Ar label2 .Op Fl L | Fl Fl label Ar label3 .Ar file1 file2 file3 .Nm .Op Fl Fl help .Op Fl Fl version .Sh DESCRIPTION The .Nm utility compares the contents of three different versions of a file, .Ar file1 , .Ar file2 and .Ar file3 , writing the result to the standard output. The options describe different methods of merging and purging the separate versions into a new file. .Nm is used by .Xr rcs 1 to merge specific versions or create new versions.
p The options are as follows: l -tag -width "-E, -X" t Fl 3 , Fl Fl easy-only Produces an output script suitable for .Xr ed 1 with changes specific only to .Ar file3 . t Fl A Fl Fl show-all Output all changes, bracketing conflicts. t Fl a , Fl Fl text Treat all files as ASCII. t Fl E , Fl Fl show-overlap t Fl X Similar to .Fl e and .Fl x , respectively, but treat overlapping changes (i.e., changes that would be noted with ==== in the normal listing) differently. The overlapping lines from both files will be inserted by the edit script, bracketed by "<<<<<<" and ">>>>>>" lines. t Fl e , Fl Fl ed Produces output in a form suitable as an input script for the .Xr ed 1 utility. The script may then be used to merge differences common between all three files and differences specific to .Ar file1 and .Ar file3 . In other words, the .Fl e option ignores differences specific to .Ar file1 and .Ar file2 , and those specific to .Ar file2 and .Ar file3 . It is useful for backing out changes specific to .Ar file2 only. t Fl Fl help Prints usage information and exits. t Fl i Appends 'w' and 'q' .Xr ed 1 commands. t Fl L , Fl Fl label Defines labels to print instead of file names .Ar file1 , .Ar file2 and .Ar file3 . t Fl m, Fl Fl merge Merge output instead of generating ed script. t Fl T, Fl Fl initial-tab In the normal listing, use a tab instead of two spaces at the beginning of each line. In modes that produce an .Xr ed 1 script, this option changes nothing. t Fl x, Fl Fl overlap-only Produces an output script suitable for .Xr ed 1 with changes specific only to all three versions. t Fl Fl diff-program Ar program Use .Ar program instead of the default .Xr diff 1 to compare files. t Fl Fl strip-trailing-cr Strip trailing carriage return on input files. t Fl Fl version Prints version information and exits. .El
p The .Fl E option is used by .Tn RCS .Xr merge 1 to ensure that overlapping changes in the merged files are preserved and brought to someone's attention.
p For example, suppose lines 7-8 are changed in both .Ar file1 and .Ar file2 . Applying the edit script generated by the command
p .Dl $ diff3 -E file1 file2 file3
p to .Ar file1 results in the file: d -literal -offset indent lines 1-6 of file1 <<<<<<< file1 lines 7-8 of file1 ======= lines 7-8 of file3 >>>>>>> file3 rest of file1 .Ed
p The default output of .Nm 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 .Xr ed 1 to create the desired target from the different versions. See .Xr diff 1 for a description of the commands. l -tag -width "=====" t Li ==== The lines beneath this notation are ranges of lines which are different between all files. t ==== Ns Va n The lines beneath this notation are ranges of lines which are exclusively different in file .Va n . .El .Sh SEE ALSO .Xr diff 1 , .Xr ed 1 , .Xr merge 1 , .Xr rcs 1 , .Xr sdiff 1 .Sh HISTORY A .Nm command appeared in .At v7 . .Sh BUGS The .Fl e option cannot catch and change lines which have .Ql . as the first and only character on the line. The resulting script will fail on that line as .Ql . is an .Xr ed 1 editing command.