1DIFF(1) GNU Tools DIFF(1)
2
6 diff - find differences between two files
7
9 diff [options] from-file to-file
10
12 In the simplest case, diff compares the contents of the two files from-
13 file and to-file. A file name of - stands for text read from the stan‐
14 dard input. As a special case, diff - - compares a copy of standard
15 input to itself.
16 If from-file is a directory and to-file is not, diff compares the file
18 in from-file whose file name is that of to-file, and vice versa. The
19 non-directory file must not be -.
20 If both from-file and to-file are directories, diff compares corre‐
22 sponding files in both directories, in alphabetical order; this compar‐
23 ison is not recursive unless the -r or --recursive option is given.
24 diff never compares the actual contents of a directory as if it were a
25 file. The file that is fully specified may not be standard input,
26 because standard input is nameless and the notion of ``file with the
27 same name'' does not apply.
28 diff options begin with -, so normally from-file and to-file may not
30 begin with -. However, -- as an argument by itself treats the remain‐
31 ing arguments as file names even if they begin with -.
32 Options
34 Below is a summary of all of the options that GNU diff accepts. Most
35 options have two equivalent names, one of which is a single letter pre‐
36 ceded by -, and the other of which is a long name preceded by --. Mul‐
37 tiple single letter options (unless they take an argument) can be com‐
38 bined into a single command line word: -ac is equivalent to -a -c.
39 Long named options can be abbreviated to any unique prefix of their
40 name. Brackets ([ and ]) indicate that an option takes an optional
41 argument.
42 -lines Show lines (an integer) lines of context. This option does not
44 specify an output format by itself; it has no effect unless it
45 is combined with -c or -u. This option is obsolete. For proper
46 operation, patch typically needs at least two lines of context.
47 -a Treat all files as text and compare them line-by-line, even if
49 they do not seem to be text.
50 -b Ignore changes in amount of white space.
52 -B Ignore changes that just insert or delete blank lines.
54 --brief
56 Report only whether the files differ, not the details of the
57 differences.
58 -c Use the context output format.
60 -C lines
62 --context[=lines]
63 Use the context output format, showing lines (an integer) lines
64 of context, or three if lines is not given. For proper opera‐
65 tion, patch typically needs at least two lines of context.
66 --changed-group-format=format
68 Use format to output a line group containing differing lines
69 from both files in if-then-else format.
70 -d Change the algorithm to perhaps find a smaller set of changes.
72 This makes diff slower (sometimes much slower).
73 -D name
75 Make merged if-then-else format output, conditional on the pre‐
76 processor macro name.
77 -e
79 --ed Make output that is a valid ed script.
80 --exclude=pattern
82 When comparing directories, ignore files and subdirectories
83 whose basenames match pattern.
84 --exclude-from=file
86 When comparing directories, ignore files and subdirectories
87 whose basenames match any pattern contained in file.
88 --expand-tabs
90 Expand tabs to spaces in the output, to preserve the alignment
91 of tabs in the input files.
92 -f Make output that looks vaguely like an ed script but has changes
94 in the order they appear in the file.
95 -F regexp
97 In context and unified format, for each hunk of differences,
98 show some of the last preceding line that matches regexp.
99 --forward-ed
101 Make output that looks vaguely like an ed script but has changes
102 in the order they appear in the file.
103 -h This option currently has no effect; it is present for Unix com‐
105 patibility.
106 -H Use heuristics to speed handling of large files that have numer‐
108 ous scattered small changes.
109 --horizon-lines=lines
111 Do not discard the last lines lines of the common prefix and the
112 first lines lines of the common suffix.
113 -i Ignore changes in case; consider upper- and lower-case letters
115 equivalent.
116 -I regexp
118 Ignore changes that just insert or delete lines that match reg‐
119 exp.
120 --ifdef=name
122 Make merged if-then-else format output, conditional on the pre‐
123 processor macro name.
124 --ignore-all-space
126 Ignore white space when comparing lines.
127 --ignore-blank-lines
129 Ignore changes that just insert or delete blank lines.
130 --ignore-case
132 Ignore changes in case; consider upper- and lower-case to be the
133 same.
134 --ignore-matching-lines=regexp
136 Ignore changes that just insert or delete lines that match reg‐
137 exp.
138 --ignore-space-change
140 Ignore changes in amount of white space.
141 --initial-tab
143 Output a tab rather than a space before the text of a line in
144 normal or context format. This causes the alignment of tabs in
145 the line to look normal.
146 -l Pass the output through pr to paginate it.
148 -L label
150 --label=label
151 Use label instead of the file name in the context format and
152 unified format headers.
153 --left-column
155 Print only the left column of two common lines in side by side
156 format.
157 --line-format=format
159 Use format to output all input lines in in-then-else format.
160 --minimal
162 Change the algorithm to perhaps find a smaller set of changes.
163 This makes diff slower (sometimes much slower).
164 -n Output RCS-format diffs; like -f except that each command speci‐
166 fies the number of lines affected.
167 -N
169 --new-file
170 In directory comparison, if a file is found in only one direc‐
171 tory, treat it as present but empty in the other directory.
172 --new-group-format=format
174 Use format to output a group of lines taken from just the second
175 file in if-then-else format.
176 --new-line-format=format
178 Use format to output a line taken from just the second file in
179 if-then-else format.
180 --old-group-format=format
182 Use format to output a group of lines taken from just the first
183 file in if-then-else format.
184 --old-line-format=format
186 Use format to output a line taken from just the first file in
187 if-then-else format.
188 -p Show which C function each change is in.
190 -P When comparing directories, if a file appears only in the second
192 directory of the two, treat it as present but empty in the
193 other.
194 --paginate
196 Pass the output through pr to paginate it.
197 -q Report only whether the files differ, not the details of the
199 differences.
200 -r When comparing directories, recursively compare any subdirecto‐
202 ries found.
203 --rcs Output RCS-format diffs; like -f except that each command speci‐
205 fies the number of lines affected.
206 --recursive
208 When comparing directories, recursively compare any subdirecto‐
209 ries found.
210 --report-identical-files
212 -s Report when two files are the same.
213 -S file
215 When comparing directories, start with the file file. This is
216 used for resuming an aborted comparison.
217 --from-file=file
219 Compare file to all operands. file can be a directory.
220 --to-file=file
222 Compare all operands to file. file can be a directory.
223 --sdiff-merge-assist
225 Print extra information to help sdiff. sdiff uses this option
226 when it runs diff. This option is not intended for users to use
227 directly.
228 --show-c-function
230 Show which C function each change is in.
231 --show-function-line=regexp
233 In context and unified format, for each hunk of differences,
234 show some of the last preceding line that matches regexp.
235 --side-by-side
237 Use the side by side output format.
238 --speed-large-files
240 Use heuristics to speed handling of large files that have numer‐
241 ous scattered small changes.
242 --starting-file=file
244 When comparing directories, start with the file file. This is
245 used for resuming an aborted comparison.
246 --suppress-common-lines
248 Do not print common lines in side by side format.
249 -t Expand tabs to spaces in the output, to preserve the alignment
251 of tabs in the input files.
252 -T Output a tab rather than a space before the text of a line in
254 normal or context format. This causes the alignment of tabs in
255 the line to look normal.
256 --text Treat all files as text and compare them line-by-line, even if
258 they do not appear to be text.
259 -u Use the unified output format.
261 --unchanged-group-format=format
263 Use format to output a group of common lines taken from both
264 files in if-then-else format.
265 --unchanged-line-format=format
267 Use format to output a line common to both files in if-then-else
268 format.
269 --unidirectional-new-file
271 When comparing directories, if a file appears only in the second
272 directory of the two, treat it as present but empty in the
273 other.
274 -U lines
276 --unified[=lines]
277 Use the unified output format, showing lines (an integer) lines
278 of context, or three if lines is not given. For proper opera‐
279 tion, patch typically needs at least two lines of context.
280 -v
282 --version
283 Output the version number of diff.
284 -w Ignore white space when comparing lines.
286 -W columns
288 --width=columns
289 Use an output width of columns in side by side format.
290 -x pattern
292 When comparing directories, ignore files and subdirectories
293 whose basenames match pattern.
294 -X file
296 When comparing directories, ignore files and subdirectories
297 whose basenames match any pattern contained in file.
298 -y Use the side by side output format.
300
302 cmp(1), comm(1), diff3(1), ed(1), patch(1), pr(1), sdiff(1).
303
305 An exit status of 0 means no differences were found, 1 means some dif‐
306 ferences were found, and 2 means trouble.
307GNU Tools 22sep1993 DIFF(1)