1GREP(1P) POSIX Programmer's Manual GREP(1P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
13 grep — search a file for a pattern
14
16 grep [−E|−F] [−c|−l|−q] [−insvx] −e pattern_list
17 [−e pattern_list]... [−f pattern_file]... [file...]
18 grep [−E|−F] [−c|−l|−q] [−insvx] [−e pattern_list]...
20 −f pattern_file [−f pattern_file]... [file...]
21 grep [−E|−F] [−c|−l|−q] [−insvx] pattern_list [file...]
23
25 The grep utility shall search the input files, selecting lines matching
26 one or more patterns; the types of patterns are controlled by the
27 options specified. The patterns are specified by the −e option, −f
28 option, or the pattern_list operand. The pattern_list's value shall
29 consist of one or more patterns separated by <newline> characters; the
30 pattern_file's contents shall consist of one or more patterns termi‐
31 nated by a <newline> character. By default, an input line shall be
32 selected if any pattern, treated as an entire basic regular expression
33 (BRE) as described in the Base Definitions volume of POSIX.1‐2008, Sec‐
34 tion 9.3, Basic Regular Expressions, matches any part of the line
35 excluding the terminating <newline>; a null BRE shall match every line.
36 By default, each selected input line shall be written to the standard
37 output.
38 Regular expression matching shall be based on text lines. Since a <new‐
40 line> separates or terminates patterns (see the −e and −f options
41 below), regular expressions cannot contain a <newline>. Similarly,
42 since patterns are matched against individual lines (excluding the ter‐
43 minating <newline> characters) of the input, there is no way for a pat‐
44 tern to match a <newline> found in the input.
45
47 The grep utility shall conform to the Base Definitions volume of
48 POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines.
49 The following options shall be supported:
51 −E Match using extended regular expressions. Treat each pattern
53 specified as an ERE, as described in the Base Definitions
54 volume of POSIX.1‐2008, Section 9.4, Extended Regular Expres‐
55 sions. If any entire ERE pattern matches some part of an
56 input line excluding the terminating <newline>, the line
57 shall be matched. A null ERE shall match every line.
58 −F Match using fixed strings. Treat each pattern specified as a
60 string instead of a regular expression. If an input line con‐
61 tains any of the patterns as a contiguous sequence of bytes,
62 the line shall be matched. A null string shall match every
63 line.
64 −c Write only a count of selected lines to standard output.
66 −e pattern_list
68 Specify one or more patterns to be used during the search for
69 input. The application shall ensure that patterns in pat‐
70 tern_list are separated by a <newline>. A null pattern can
71 be specified by two adjacent <newline> characters in pat‐
72 tern_list. Unless the −E or −F option is also specified,
73 each pattern shall be treated as a BRE, as described in the
74 Base Definitions volume of POSIX.1‐2008, Section 9.3, Basic
75 Regular Expressions. Multiple −e and −f options shall be
76 accepted by the grep utility. All of the specified patterns
77 shall be used when matching lines, but the order of evalua‐
78 tion is unspecified.
79 −f pattern_file
81 Read one or more patterns from the file named by the pathname
82 pattern_file. Patterns in pattern_file shall be terminated
83 by a <newline>. A null pattern can be specified by an empty
84 line in pattern_file. Unless the −E or −F option is also
85 specified, each pattern shall be treated as a BRE, as
86 described in the Base Definitions volume of POSIX.1‐2008,
87 Section 9.3, Basic Regular Expressions.
88 −i Perform pattern matching in searches without regard to case;
90 see the Base Definitions volume of POSIX.1‐2008, Section 9.2,
91 Regular Expression General Requirements.
92 −l (The letter ell.) Write only the names of files containing
94 selected lines to standard output. Pathnames shall be written
95 once per file searched. If the standard input is searched, a
96 pathname of "(standardinput)" shall be written, in the POSIX
97 locale. In other locales, "standardinput" may be replaced by
98 something more appropriate in those locales.
99 −n Precede each output line by its relative line number in the
101 file, each file starting at line 1. The line number counter
102 shall be reset for each file processed.
103 −q Quiet. Nothing shall be written to the standard output,
105 regardless of matching lines. Exit with zero status if an
106 input line is selected.
107 −s Suppress the error messages ordinarily written for nonexis‐
109 tent or unreadable files. Other error messages shall not be
110 suppressed.
111 −v Select lines not matching any of the specified patterns. If
113 the −v option is not specified, selected lines shall be those
114 that match any of the specified patterns.
115 −x Consider only input lines that use all characters in the line
117 excluding the terminating <newline> to match an entire fixed
118 string or regular expression to be matching lines.
119
121 The following operands shall be supported:
122 pattern_list
124 Specify one or more patterns to be used during the search for
125 input. This operand shall be treated as if it were specified
126 as −e pattern_list.
127 file A pathname of a file to be searched for the patterns. If no
129 file operands are specified, the standard input shall be
130 used.
131
133 The standard input shall be used if no file operands are specified, and
134 shall be used if a file operand is '−' and the implementation treats
135 the '−' as meaning standard input. Otherwise, the standard input shall
136 not be used. See the INPUT FILES section.
137
139 The input files shall be text files.
140
142 The following environment variables shall affect the execution of grep:
143 LANG Provide a default value for the internationalization vari‐
145 ables that are unset or null. (See the Base Definitions vol‐
146 ume of POSIX.1‐2008, Section 8.2, Internationalization Vari‐
147 ables for the precedence of internationalization variables
148 used to determine the values of locale categories.)
149 LC_ALL If set to a non-empty string value, override the values of
151 all the other internationalization variables.
152 LC_COLLATE
154 Determine the locale for the behavior of ranges, equivalence
155 classes, and multi-character collating elements within regu‐
156 lar expressions.
157 LC_CTYPE Determine the locale for the interpretation of sequences of
159 bytes of text data as characters (for example, single-byte as
160 opposed to multi-byte characters in arguments and input
161 files) and the behavior of character classes within regular
162 expressions.
163 LC_MESSAGES
165 Determine the locale that should be used to affect the format
166 and contents of diagnostic messages written to standard
167 error.
168 NLSPATH Determine the location of message catalogs for the processing
170 of LC_MESSAGES.
171
173 Default.
174
176 If the −l option is in effect, the following shall be written for each
177 file containing at least one selected input line:
178 "%s\n", <file>
180 Otherwise, if more than one file argument appears, and −q is not speci‐
182 fied, the grep utility shall prefix each output line by:
183 "%s:", <file>
185 The remainder of each output line shall depend on the other options
187 specified:
188 * If the −c option is in effect, the remainder of each output line
190 shall contain:
191 "%d\n", <count>
193 * Otherwise, if −c is not in effect and the −n option is in effect,
195 the following shall be written to standard output:
196 "%d:", <line number>
198 * Finally, the following shall be written to standard output:
200 "%s", <selected-line contents>
202
204 The standard error shall be used only for diagnostic messages.
205
207 None.
208
210 None.
211
213 The following exit values shall be returned:
214 0 One or more lines were selected.
216 1 No lines were selected.
218 >1 An error occurred.
220
222 If the −q option is specified, the exit status shall be zero if an
223 input line is selected, even if an error was detected. Otherwise,
224 default actions shall be performed.
225 The following sections are informative.
227
229 Care should be taken when using characters in pattern_list that may
230 also be meaningful to the command interpreter. It is safest to enclose
231 the entire pattern_list argument in single-quotes:
232 '...'
234 The −e pattern_list option has the same effect as the pattern_list op‐
236 erand, but is useful when pattern_list begins with the <hyphen> delim‐
237 iter. It is also useful when it is more convenient to provide multiple
238 patterns as separate arguments.
239 Multiple −e and −f options are accepted and grep uses all of the pat‐
241 terns it is given while matching input text lines. (Note that the
242 order of evaluation is not specified. If an implementation finds a null
243 string as a pattern, it is allowed to use that pattern first, matching
244 every line, and effectively ignore any other patterns.)
245 The −q option provides a means of easily determining whether or not a
247 pattern (or string) exists in a group of files. When searching several
248 files, it provides a performance improvement (because it can quit as
249 soon as it finds the first match) and requires less care by the user in
250 choosing the set of files to supply as arguments (because it exits zero
251 if it finds a match even if grep detected an access or read error on
252 earlier file operands).
253
255 1. To find all uses of the word "Posix" (in any case) in file text.mm
256 and write with line numbers:
257 grep −i −n posix text.mm
259 2. To find all empty lines in the standard input:
261 grep ^$
263 or:
265 grep −v .
267 3. Both of the following commands print all lines containing strings
269 "abc" or "def" or both:
270 grep −E 'abc|def'
272 grep −F 'abc
274 def'
275 4. Both of the following commands print all lines matching exactly
277 "abc" or "def":
278 grep −E '^abc$|^def$'
280 grep −F −x 'abc
282 def'
283
285 This grep has been enhanced in an upwards-compatible way to provide the
286 exact functionality of the historical egrep and fgrep commands as well.
287 It was the clear intention of the standard developers to consolidate
288 the three greps into a single command.
289 The old egrep and fgrep commands are likely to be supported for many
291 years to come as implementation extensions, allowing historical appli‐
292 cations to operate unmodified.
293 Historical implementations usually silently ignored all but one of mul‐
295 tiply-specified −e and −f options, but were not consistent as to which
296 specification was actually used.
297 The −b option was omitted from the OPTIONS section because block num‐
299 bers are implementation-defined.
300 The System V restriction on using − to mean standard input was omitted.
302 A definition of action taken when given a null BRE or ERE is specified.
304 This is an error condition in some historical implementations.
305 The −l option previously indicated that its use was undefined when no
307 files were explicitly named. This behavior was historical and placed an
308 unnecessary restriction on future implementations. It has been removed.
309 The historical BSD grep −s option practice is easily duplicated by
311 redirecting standard output to /dev/null. The −s option required here
312 is from System V.
313 The −x option, historically available only with fgrep, is available
315 here for all of the non-obsolescent versions.
316
318 None.
319
321 sed
322 The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
324 Variables, Chapter 9, Regular Expressions, Section 12.2, Utility Syntax
325 Guidelines
326
328 Portions of this text are reprinted and reproduced in electronic form
329 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
330 -- Portable Operating System Interface (POSIX), The Open Group Base
331 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
332 cal and Electronics Engineers, Inc and The Open Group. (This is
333 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
334 event of any discrepancy between this version and the original IEEE and
335 The Open Group Standard, the original IEEE and The Open Group Standard
336 is the referee document. The original Standard can be obtained online
337 at http://www.unix.org/online.html .
338 Any typographical or formatting errors that appear in this page are
340 most likely to have been introduced during the conversion of the source
341 files to man page format. To report such errors, see https://www.ker‐
342 nel.org/doc/man-pages/reporting_bugs.html .
343IEEE/The Open Group 2013 GREP(1P)