diff —
differential file and directory comparator
diff |
[ -abdipTtw
]
[-c |
-e |
-f |
-n |
-q |
-u
]
[-I
pattern
]
[-L
label
]
file1 file2 |
diff |
[ -abdilpTtw
]
[-I
pattern
]
[-L
label
]
-C
number file1
file2 |
diff |
[ -abdiltw
]
[-I
pattern
]
-D
string file1
file2 |
diff |
[ -abdilpTtw
]
[-I
pattern
]
[-L
label
]
-U
number file1
file2 |
diff |
[ -abdilNPprsTtw
]
[-c |
-e |
-f |
-n |
-q |
-u
]
[-I
pattern
]
[-L label
]
[-S name
]
[-X file
]
[-x pattern
]
dir1 dir2 |
The
diff utility compares the contents of
file1 and
file2 and writes to the standard output the
list of changes necessary to convert one file into the other. No output is
produced if the files are identical.
Output options (mutually exclusive):
-
-
-C
number- Like
-c but produces a diff with
number lines of context.
-
-
-c- Produces a diff with 3 lines of context. With
-c the output format is modified
slightly: the output begins with identification of the files involved and
their creation dates and then each change is separated by a line with
fifteen *'s. The lines removed from
file1 are marked with
‘- ’; those added to
file2 are marked
‘+ ’. Lines which are changed from one file to the
other are marked in both files with ‘! ’. Changes
which lie within 3 lines of each other are grouped together on
output.
-
-
-D
string- Creates a merged version of file1 and
file2 on the standard output, with C
preprocessor controls included so that a compilation of the result without
defining string is equivalent to
compiling file1, while defining
string will yield
file2.
-
-
-e- Produces output in a form suitable as input for the editor utility,
ed(1), which can then be used to
convert file1 into file2.
Extra commands are added to the output when comparing directories with
-e, so that the result is a
sh(1) script for converting text
files which are common to the two directories from their state in
dir1 to their state in
dir2.
-
-
-f- Identical output to that of the
-e
flag, but in reverse order. It cannot be digested by
ed(1).
-
-
-n- Produces a script similar to that of
-e, but in the opposite order and with
a count of changed lines on each insert or delete command. This is the
form used by
rcsdiff(1).
-
-
-q- Just print a line when the files differ. Does not output a list of
changes.
-
-
-U
number- Like
-u but produces a diff with
number lines of context.
-
-
-u- Produces a unified diff with 3 lines of
context. A unified diff is similar to the context diff produced by the
-c option. However, unlike with
-c, all lines to be changed (added
and/or removed) are present in a single section.
Comparison options:
-
-
-a- Treat all files as ASCII text. Normally
diff will simply print “Binary
files ... differ” if files contain binary characters. Use of this
option forces diff to produce a
diff.
-
-
-b- Causes trailing blanks (spaces and tabs) to be ignored, and other strings
of blanks to compare equal.
-
-
-d- Try very hard to produce a diff as small as possible. This may consume a
lot of processing power and memory when processing large files with many
changes.
-
-
-I
pattern- Ignores changes, insertions, and deletions whose lines match the extended
regular expression pattern. Multiple
-I patterns may be specified. All lines
in the change must match some pattern for the change to be ignored. See
re_format(7) for more
information on regular expression patterns.
-
-
-i- Ignores the case of letters. E.g., “A” will compare equal to
“a”.
-
-
-L
label- Print label instead of the first (and
second, if this option is specified twice) file name and time in the
context or unified diff header.
-
-
-p- With unified and context diffs, show with each change the first 40
characters of the last line before the context beginning with a letter, an
underscore or a dollar sign. For C source code following standard layout
conventions, this will show the prototype of the function the change
applies to.
-
-
-T- Print a tab rather than a space before the rest of the line for the
normal, context or unified output formats. This makes the alignment of
tabs in the line consistent.
-
-
-t- Will expand tabs in output lines. Normal or
-c output adds character(s) to the
front of each line which may screw up the indentation of the original
source lines and make the output listing difficult to interpret. This
option will preserve the original source's indentation.
-
-
-w- Is similar to
-b but causes whitespace
(blanks and tabs) to be totally ignored. E.g., “if ( a == b
)” will compare equal to “if(a==b)”.
Directory comparison options:
-
-
-N- If a file is found in only one directory, act as if it was found in the
other directory too but was of zero size.
-
-
-P- If a file is found only in dir2, act as
if it was found in dir1 too but was of
zero size.
-
-
-r- Causes application of
diff recursively
to common subdirectories encountered.
-
-
-S
name- Re-starts a directory
diff in the
middle, beginning with file name.
-
-
-s- Causes
diff to report files which are
the same, which are otherwise not mentioned.
-
-
-X
file- Exclude files and subdirectories from comparison whose basenames match
lines in file. Multiple
-X options may be specified.
-
-
-x
pattern- Exclude files and subdirectories from comparison whose basenames match
pattern. Patterns are matched using
shell-style globbing via
fnmatch(3). Multiple
-x options may be specified.
If both arguments are directories,
diff sorts
the contents of the directories by name, and then runs the regular file
diff algorithm, producing a change list, on
text files which are different. Binary files which differ, common
subdirectories, and files which appear in only one directory are described as
such. In directory mode only regular files and directories are compared. If a
non-regular file such as a device special file or FIFO is encountered, a
diagnostic message is printed.
If only one of
file1 and
file2 is a directory,
diff is applied to the non-directory file
and the file contained in the directory file with a filename that is the same
as the last component of the non-directory file.
If either
file1 or
file2 is ‘-’, the standard
input is used in its place.
The default (without
-e,
-c, or
-n options) output contains lines of these
forms, where
XX,
YY,
ZZ,
QQ are line numbers respective of file order.
XXaYY- At (the end of) line XX of
file1, append the contents of line
YY of
file2 to make them equal.
XXaYY,ZZ- Same as above, but append the range of lines,
YY through
ZZ of
file2 to line
XX of file1.
XXdYY- At line XX delete the line. The value
YY tells to which line the change would
bring file1 in line with
file2.
XX,YYdZZ- Delete the range of lines XX through
YY in
file1.
XXcYY- Change the line XX in
file1 to the line
YY in
file2.
XX,YYcZZ- Replace the range of specified lines with the line
ZZ.
XX,YYcZZ,QQ- Replace the range
XX,YY
from file1 with the range
ZZ,QQ
from file2.
These lines resemble
ed(1) subcommands
to convert
file1 into
file2. The line numbers before the action
letters pertain to
file1; those after pertain
to
file2. Thus, by exchanging
a for
d
and reading the line in reverse order, one can also determine how to convert
file2 into
file1. As in
ed(1), identical pairs (where num1 =
num2) are abbreviated as a single number.
- /tmp/diff.XXXXXXXX
- Temporary file used when comparing a device or the standard input. Note
that the temporary file is unlinked as soon as it is created so it will
not show up in a directory listing.
The
diff utility exits with one of the
following values:
- 0
- No differences were found.
- 1
- Differences were found.
- >1
- An error occurred.
cmp(1),
comm(1),
diff3(1),
ed(1),
patch(1),
sdiff(1)
James W. Hunt and
M. Douglas McIlroy, An Algorithm
for Differential File Comparison, Computing Science
Technical Report, Bell Laboratories 41,
June 1976.
The
diff utility is compliant with the
IEEE Std 1003.1-2008
(“POSIX.1”) specification.
The flags
[
-aDdIiLlNnPpqSsTtwXx
]
are extensions to that specification.
A
diff command appeared in
Version 6 AT&T UNIX.
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