NAME
diff
—
differential file and directory
comparator
SYNOPSIS
diff |
[-abdipTtw ] [-c |
-e | -f |
-n | -q |
-u ] [-I
pattern] [-L
label] file1 file2 |
diff |
[-abdipTtw ] [-I
pattern] [-L
label] -C
number file1 file2 |
diff |
[-abditw ] [-I
pattern] -D
string file1 file2 |
diff |
[-abdipTtw ] [-I
pattern] [-L
label] -U
number file1 file2 |
diff |
[-abdiNPprsTtw ] [-c |
-e | -f |
-n | -q |
-u ] [-I
pattern]
[-L label]
[-S name]
[-X file]
[-x pattern]
dir1 dir2 |
DESCRIPTION
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 forcesdiff
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.
Output Style
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.
XX
a
YY
- At (the end of) line XX of file1, append the contents of line YY of file2 to make them equal.
XX
a
YY,ZZ
- Same as above, but append the range of lines, YY through ZZ of file2 to line XX of file1.
XX
d
YY
- At line XX delete the line. The value YY tells to which line the change would bring file1 in line with file2.
XX,YY
d
ZZ
- Delete the range of lines XX through YY in file1.
XX
c
YY
- Change the line XX in file1 to the line YY in file2.
XX,YY
c
ZZ
- Replace the range of specified lines with the line ZZ.
XX,YY
c
ZZ,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.
FILES
- /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.
EXIT STATUS
The diff
utility exits with one of the
following values:
- 0
- No differences were found.
- 1
- Differences were found.
- >1
- An error occurred.
SEE ALSO
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, AT&T Bell Laboratories, Computing Science Technical Report, 41, June 1976.
STANDARDS
The diff
utility is compliant with the
IEEE Std 1003.1-2008 (“POSIX.1”)
specification.
The flags [-aDdIiLNnPpqSsTtwXx
] are
extensions to that specification.
HISTORY
A diff
command appeared in
Version 5 AT&T UNIX.