1GREP(P) POSIX Programmer's Manual GREP(P)
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6 grep - search a file for a pattern
7
9 grep [-E| -F][-c| -l| -q][-insvx] -e pattern_list...
10 [-f pattern_file]...[file...]
11 grep [-E| -F][-c| -l| -q][-insvx][-e pattern_list]...
13 -f pattern_file...[file...]
14 grep [-E| -F][-c| -l| -q][-insvx] pattern_list[file...]
16
19 The grep utility shall search the input files, selecting lines matching
20 one or more patterns; the types of patterns are controlled by the
21 options specified. The patterns are specified by the -e option, -f
22 option, or the pattern_list operand. The pattern_list's value shall
23 consist of one or more patterns separated by <newline>s; the pat‐
24 tern_file's contents shall consist of one or more patterns terminated
25 by <newline>. By default, an input line shall be selected if any pat‐
26 tern, treated as an entire basic regular expression (BRE) as described
27 in the Base Definitions volume of IEEE Std 1003.1-2001, Section 9.3,
28 Basic Regular Expressions, matches any part of the line excluding the
29 terminating <newline>; a null BRE shall match every line. By default,
30 each selected input line shall be written to the standard output.
31 Regular expression matching shall be based on text lines. Since a <new‐
33 line> separates or terminates patterns (see the -e and -f options
34 below), regular expressions cannot contain a <newline>. Similarly,
35 since patterns are matched against individual lines (excluding the ter‐
36 minating <newline>s) of the input, there is no way for a pattern to
37 match a <newline> found in the input.
38
40 The grep utility shall conform to the Base Definitions volume of
41 IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
42 The following options shall be supported:
44 -E Match using extended regular expressions. Treat each pattern
46 specified as an ERE, as described in the Base Definitions volume
47 of IEEE Std 1003.1-2001, Section 9.4, Extended Regular Expres‐
48 sions. If any entire ERE pattern matches some part of an input
49 line excluding the terminating <newline>, the line shall be
50 matched. A null ERE shall match every line.
51 -F Match using fixed strings. Treat each pattern specified as a
53 string instead of a regular expression. If an input line con‐
54 tains any of the patterns as a contiguous sequence of bytes, the
55 line shall be matched. A null string shall match every line.
56 -c Write only a count of selected lines to standard output.
58 -e pattern_list
60 Specify one or more patterns to be used during the search for
62 input. The application shall ensure that patterns in pat‐
63 tern_list are separated by a <newline>. A null pattern can be
64 specified by two adjacent <newline>s in pattern_list. Unless the
65 -E or -F option is also specified, each pattern shall be treated
66 as a BRE, as described in the Base Definitions volume of
67 IEEE Std 1003.1-2001, Section 9.3, Basic Regular Expressions.
68 Multiple -e and -f options shall be accepted by the grep util‐
69 ity. All of the specified patterns shall be used when matching
70 lines, but the order of evaluation is unspecified.
71 -f pattern_file
73 Read one or more patterns from the file named by the pathname
75 pattern_file. Patterns in pattern_file shall be terminated by a
76 <newline>. A null pattern can be specified by an empty line in
77 pattern_file. Unless the -E or -F option is also specified, each
78 pattern shall be treated as a BRE, as described in the Base Def‐
79 initions volume of IEEE Std 1003.1-2001, Section 9.3, Basic Reg‐
80 ular Expressions.
81 -i Perform pattern matching in searches without regard to case; see
83 the Base Definitions volume of IEEE Std 1003.1-2001, Section
84 9.2, Regular Expression General Requirements.
85 -l (The letter ell.) Write only the names of files containing
87 selected lines to standard output. Pathnames shall be written
88 once per file searched. If the standard input is searched, a
89 pathname of "(standard input)" shall be written, in the POSIX
90 locale. In other locales, "standard input" may be replaced by
91 something more appropriate in those locales.
92 -n Precede each output line by its relative line number in the
94 file, each file starting at line 1. The line number counter
95 shall be reset for each file processed.
96 -q Quiet. Nothing shall be written to the standard output, regard‐
98 less of matching lines. Exit with zero status if an input line
99 is selected.
100 -s Suppress the error messages ordinarily written for nonexistent
102 or unreadable files. Other error messages shall not be sup‐
103 pressed.
104 -v Select lines not matching any of the specified patterns. If the
106 -v option is not specified, selected lines shall be those that
107 match any of the specified patterns.
108 -x Consider only input lines that use all characters in the line
110 excluding the terminating <newline> to match an entire fixed
111 string or regular expression to be matching lines.
112
115 The following operands shall be supported:
116 pattern_list
118 Specify one or more patterns to be used during the search for
119 input. This operand shall be treated as if it were specified as
120 -e pattern_list.
121 file A pathname of a file to be searched for the patterns. If no file
123 operands are specified, the standard input shall be used.
124
127 The standard input shall be used only if no file operands are speci‐
128 fied. See the INPUT FILES section.
129
131 The input files shall be text files.
132
134 The following environment variables shall affect the execution of grep:
135 LANG Provide a default value for the internationalization variables
137 that are unset or null. (See the Base Definitions volume of
138 IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari‐
139 ables for the precedence of internationalization variables used
140 to determine the values of locale categories.)
141 LC_ALL If set to a non-empty string value, override the values of all
143 the other internationalization variables.
144 LC_COLLATE
146 Determine the locale for the behavior of ranges, equivalence
148 classes, and multi-character collating elements within regular
149 expressions.
150 LC_CTYPE
152 Determine the locale for the interpretation of sequences of
153 bytes of text data as characters (for example, single-byte as
154 opposed to multi-byte characters in arguments and input files)
155 and the behavior of character classes within regular expres‐
156 sions.
157 LC_MESSAGES
159 Determine the locale that should be used to affect the format
160 and contents of diagnostic messages written to standard error.
161 NLSPATH
163 Determine the location of message catalogs for the processing of
164 LC_MESSAGES .
165
168 Default.
169
171 If the -l option is in effect, and the -q option is not, the following
172 shall be written for each file containing at least one selected input
173 line:
174 "%s\n", <file>
177 Otherwise, if more than one file argument appears, and -q is not speci‐
179 fied, the grep utility shall prefix each output line by:
180 "%s:", <file>
183 The remainder of each output line shall depend on the other options
185 specified:
186 * If the -c option is in effect, the remainder of each output line
188 shall contain:
189 "%d\n", <count>
192 * Otherwise, if -c is not in effect and the -n option is in effect,
194 the following shall be written to standard output:
195 "%d:", <line number>
198 * Finally, the following shall be written to standard output:
200 "%s", <selected-line contents>
203
205 The standard error shall be used only for diagnostic messages.
206
208 None.
209
211 None.
212
214 The following exit values shall be returned:
215 0 One or more lines were selected.
217 1 No lines were selected.
219 >1 An error occurred.
221
224 If the -q option is specified, the exit status shall be zero if an
225 input line is selected, even if an error was detected. Otherwise,
226 default actions shall be performed.
227 The following sections are informative.
229
231 Care should be taken when using characters in pattern_list that may
232 also be meaningful to the command interpreter. It is safest to enclose
233 the entire pattern_list argument in single quotes:
234 '...'
237 The -e pattern_list option has the same effect as the pattern_list op‐
239 erand, but is useful when pattern_list begins with the hyphen delim‐
240 iter. It is also useful when it is more convenient to provide multiple
241 patterns as separate arguments.
242 Multiple -e and -f options are accepted and grep uses all of the pat‐
244 terns it is given while matching input text lines. (Note that the order
245 of evaluation is not specified. If an implementation finds a null
246 string as a pattern, it is allowed to use that pattern first, matching
247 every line, and effectively ignore any other patterns.)
248 The -q option provides a means of easily determining whether or not a
250 pattern (or string) exists in a group of files. When searching several
251 files, it provides a performance improvement (because it can quit as
252 soon as it finds the first match) and requires less care by the user in
253 choosing the set of files to supply as arguments (because it exits zero
254 if it finds a match even if grep detected an access or read error on
255 earlier file operands).
256
258 1. To find all uses of the word "Posix" (in any case) in file text.mm
259 and write with line numbers:
260 grep -i -n posix text.mm
263 2. To find all empty lines in the standard input:
265 grep ^$
268 or:
270 grep -v .
273 3. Both of the following commands print all lines containing strings
275 "abc" or "def" or both:
276 grep -E 'abc|def'
279 grep -F 'abc
282 def'
283 4. Both of the following commands print all lines matching exactly
285 "abc" or "def" :
286 grep -E '^abc$|^def$'
289 grep -F -x 'abc
292 def'
293
295 This grep has been enhanced in an upwards-compatible way to provide the
296 exact functionality of the historical egrep and fgrep commands as well.
297 It was the clear intention of the standard developers to consolidate
298 the three greps into a single command.
299 The old egrep and fgrep commands are likely to be supported for many
301 years to come as implementation extensions, allowing historical appli‐
302 cations to operate unmodified.
303 Historical implementations usually silently ignored all but one of mul‐
305 tiply-specified -e and -f options, but were not consistent as to which
306 specification was actually used.
307 The -b option was omitted from the OPTIONS section because block num‐
309 bers are implementation-defined.
310 The System V restriction on using - to mean standard input was omitted.
312 A definition of action taken when given a null BRE or ERE is specified.
314 This is an error condition in some historical implementations.
315 The -l option previously indicated that its use was undefined when no
317 files were explicitly named. This behavior was historical and placed an
318 unnecessary restriction on future implementations. It has been
319 removed.
320 The historical BSD grep -s option practice is easily duplicated by
322 redirecting standard output to /dev/null. The -s option required here
323 is from System V.
324 The -x option, historically available only with fgrep, is available
326 here for all of the non-obsolescent versions.
327
329 None.
330
332 sed
333
335 Portions of this text are reprinted and reproduced in electronic form
336 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
337 -- Portable Operating System Interface (POSIX), The Open Group Base
338 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
339 Electrical and Electronics Engineers, Inc and The Open Group. In the
340 event of any discrepancy between this version and the original IEEE and
341 The Open Group Standard, the original IEEE and The Open Group Standard
342 is the referee document. The original Standard can be obtained online
343 at http://www.opengroup.org/unix/online.html .
344IEEE/The Open Group 2003 GREP(P)