DIFF(1)DIFF(1)
NAME
diff – differential file comparator
SYNOPSIS
diff
[
-abcefmnruw
]
file1 ... file2
DESCRIPTION
Diff
tells what lines must be changed in two files to bring them
into agreement.
If one file
is a directory,
then a file in that directory with basename the same as that of
the other file is used.
If both files are directories, similarly named files in the
two directories are compared by the method of
diff
for text
files and
cmp(1)
otherwise.
If more than two file names are given, then each argument is compared
to the last argument as above.
The
-r
option causes
diff
to process similarly named subdirectories recursively.
When processing more than one file,
diff
prefixes file differences with a single line
listing the two differing files, in the form of
a
diff
command line.
The
-m
flag causes this behavior even when processing single files.
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 abbreviated 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
-w
option causes all white-space to be removed from input lines
before applying the difference algorithm.
The
-n
option prefixes each range with
file:
and inserts a space around the
a,
c,
and
d
verbs.
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. It may, however, be
useful as input to a stream-oriented post-processor.
The
-c
option includes three lines of context around each
change, merging changes whose contexts overlap.
In this mode,
diff
prints
-
and
+
instead of
<
and
>
because the former are easier to distinguish when mixed.
The
-a
flag displays the entire file as context.
The
-u
option provides a unix-compatible unified diff.
This format is similar to that provided by
-c.
However, the
+
and
-
prefixes are not separated from the rest of the line by spaces,
and the file header is in the following format:
--- filename.old
+++ filename.new
@@ -line,len +line,len @@
Except in rare circumstances,
diff
finds a smallest sufficient set of file
differences.
FILES
/tmp/diff[12]
SOURCE
/sys/src/cmd/diff
SEE ALSO
cmp(1),
comm(1),
ed(1),
idiff(1)
DIAGNOSTICS
Exit status is the empty string
for no differences,
some
for some,
and
error
for trouble.
BUGS
Editing scripts produced under the
-e or
-f option are naive about
creating lines consisting of a single ‘.’.
When running
diff
on directories, the notion of what is a text
file is open to debate.