'\"macro stdmacro
.if n .pH g1.diff3 @(#)diff3	30.2 of 12/25/85
.nr X
.if \nX=0 .ds x} DIFF3 1 "Directory and File Management Utilities" "\&"
.if \nX=1 .ds x} DIFF3 1 "Directory and File Management Utilities"
.if \nX=2 .ds x} DIFF3 1 "" "\&"
.if \nX=3 .ds x} DIFF3 "" "" "\&"
.TH \*(x}
.SH NAME
diff3 \- 3-way differential file comparison
.SH SYNOPSIS
.B diff3
[
.B \-exEX3
.RB [ \-i " | " -m ]
.RB [ -L
label1
.B -L
label3]
]
file1 file2 file3
.SH DESCRIPTION
.I Diff3
compares three versions of a file,
and publishes disagreeing ranges of text
flagged with these codes:
.TP 16
====
all three files differ
.TP 16
====1
.IR file1 " is different"
.TP 16
====2
.IR file2 " is different"
.TP 16
====3
.IR file3 " is different"
.PP
The type of change suffered in converting a given range
of a given file to some other is
indicated in one of these ways:
.TP 16
.IB f " : " n1 " a"
Text is to be appended after line number
.I n1
in file
.I f,
where
.I f
= 1, 2, or 3.
.TP 16
.IB f " : " n1 " , " n2 " c"
Text is to be
changed in the range line
.I n1
to line
.IR n2 .
If 
.I n1
=
.I n2,
the range may be abbreviated to
.IR n1 .
.PP
The original contents of the range follows immediately
after a
.B c
indication.
When the contents of two
files are identical, the contents of the lower-numbered
file is suppressed.
.PP
The
.B \-m
option produces a merge script
on the output of
.IR diff3 .
If none of
.B \-eExX3
is specified along with
.BR \-m ,
then the format of option
.B \-E
is presumed.
If the
.B \-m
option is used,
then binary files, files without
trailing newline, and files with
excessively long lines can be
successfully merged.
.PP
If no
.B \-m
option is specified, then
under the
.B \-e
option,
.I diff3
publishes a script for the editor
.IR ed (1)
that will incorporate into
.I file1
all changes between
.I file2
and
.I file3,
.IR i.e .
the changes that normally would be flagged ==== and ====3.
Option
.B \-x
(\f3\-3\f1)
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.
.PP
.ti 16n
(cat script; echo \(fm1,$p\(fm) \(bv ed \- file1
.PP
The
.B \-E
and
.B \-X
are similar to
.B \-e
and
.BR \-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.
.PP
For example, suppose lines 7-8 are changed in both file1 and file3.
The merged output of the command
.sp
.ce
"diff3 -m file1 file2 file3" 
.br
contains:
.RS
.nf

lines 1-6 of file1
<<<<<<< file1
lines 7-8 of file1
=======
lines 7-8 of file3
>>>>>>> file3
rest of file1
.fi
.RE
.PP
If there are overlaps, the user should edit the result and delete one of the
alternatives.
If the
.BI \-L "\ label1"
and
.BI \-L "\ label3"
options are given, the labels are output in place of the names
.I file1
and
.I file3
in overlap reports.
.PP
If the option
.B \-i
is specified along with one of the options
.BR \-exEX3 ,
then the resulting edit script has the editor
commands
.sp
.nf
		w
		q
.fi
.PP
added at the end.
Then the following command will update
`file1' in place with the changes.
.PP
.ti 16n
ed \- file1 < script
.SH "SEE ALSO"
diff(1),
ed(1).
.SH BUGS
If merges are done by generating explicit scripts
to input to the editor, rather than by using the
.B \-m
option, the merge is limited by the capabilities
of the editor
.IR ed (1).
The editor cannot handle excessively long lines,
binary files (with nul bytes)
or files without a trailing newline.
.SH DIAGNOSTICS
An exit status of 0 means
.I diff3
was successful,
1 means some overlaps were found,
and 2 means trouble.
.\"	@(#)diff3.1	6.2 of 9/2/83
.Ee
'\".so /pubs/tools/origin.bsd