2 .\" $FreeBSD: src/gnu/usr.bin/grep/grep.1,v 1.16.2.3 2001/11/27 08:25:45 ru Exp $
3 .\" $DragonFly: src/gnu/usr.bin/grep/grep.1,v 1.3 2005/10/08 11:28:23 corecode Exp $
7 . if \w'\(lq' .ds lq "\(lq
11 . if \w'\(rq' .ds rq "\(rq
17 .Id $Id: grep.1,v 1.9 2000/01/26 03:42:16 alainm Exp $
18 .TH GREP 1 \*(Dt "GNU Project"
20 grep, egrep, fgrep, zgrep \- print lines matching a pattern
37 searches the named input
39 (or standard input if no files are named, or
43 for lines containing a match to the given
47 prints the matching lines.
49 In addition, two variant programs
65 .BI \-A " NUM" "\fR,\fP \-\^\-after-context=" NUM
68 lines of trailing context after matching lines.
70 .BR \-a ", " \-\^\-text
71 Process a binary file as if it were text; this is equivalent to the
72 .B \-\^\-binary-files=text
75 .BI \-B " NUM" "\fR,\fP \-\^\-before-context=" NUM
78 lines of leading context before matching lines.
80 \fB\-C\fP [\fINUM\fP], \fB\-\fP\fINUM\fP, \fB\-\^\-context\fP[\fB=\fP\fINUM\fP]
83 lines (default 2) of output context.
85 .BR \-b ", " \-\^\-byte-offset
86 Print the byte offset within the input file before
89 .BI \-\^\-binary-files= TYPE
90 If the first few bytes of a file indicate that the file contains binary
91 data, assume that the file is of type
99 normally outputs either
100 a one-line message saying that a binary file matches, or no message if
107 assumes that a binary file does not match; this is equivalent to the
115 processes a binary file as if it were text; this is equivalent to the
119 .B "grep \-\^\-binary-files=text"
120 might output binary garbage,
121 which can have nasty side effects if the output is a terminal and if the
122 terminal driver interprets some of it as commands.
124 .BR \-c ", " \-\^\-count
125 Suppress normal output; instead print a count of
126 matching lines for each input file.
128 .BR \-v ", " \-\^\-invert-match
129 option (see below), count non-matching lines.
131 .BI \-d " ACTION" "\fR,\fP \-\^\-directories=" ACTION
132 If an input file is a directory, use
134 to process it. By default,
138 which means that directories are read just as if they were ordinary files.
143 directories are silently skipped.
149 grep reads all files under each directory, recursively;
150 this is equivalent to the
154 .BR \-E ", " \-\^\-extended-regexp
157 as an extended regular expression (see below).
159 .BI \-e " PATTERN" "\fR,\fP \-\^\-regexp=" PATTERN
162 as the pattern; useful to protect patterns beginning with
165 .BR \-F ", " \-\^\-fixed-strings
168 as a list of fixed strings, separated by newlines,
169 any of which is to be matched.
171 .BI \-f " FILE" "\fR,\fP \-\^\-file=" FILE
175 The empty file contains zero patterns, and therfore matches nothing.
177 .BR \-G ", " \-\^\-basic-regexp
180 as a basic regular expression (see below). This is the default.
182 .BR \-H ", " \-\^\-with-filename
183 Print the filename for each match.
185 .BR \-h ", " \-\^\-no-filename
186 Suppress the prefixing of filenames on output
187 when multiple files are searched.
190 Output a brief help message.
193 Process a binary file as if it did not contain matching data; this is
195 .B \-\^\-binary-files=without-match
198 .BR \-i ", " \-\^\-ignore-case
199 Ignore case distinctions in both the
203 .BR \-L ", " \-\^\-files-without-match
204 Suppress normal output; instead print the name
205 of each input file from which no output would
206 normally have been printed. The scanning will stop
209 .BR \-l ", " \-\^\-files-with-matches
210 Suppress normal output; instead print
211 the name of each input file from which output
212 would normally have been printed. The scanning will
213 stop on the first match.
218 system call to read input, instead of
221 system call. In some situations,
223 yields better performance. However,
225 can cause undefined behavior (including core dumps)
226 if an input file shrinks while
228 is operating, or if an I/O error occurs.
230 .BR \-n ", " \-\^\-line-number
231 Prefix each line of output with the line number
232 within its input file.
234 .BR \-q ", " \-\^\-quiet ", " \-\^\-silent
235 Quiet; suppress normal output. The scanning will stop
243 .BR \-r ", " \-\^\-recursive
244 Read all files under each directory, recursively;
245 this is equivalent to the
249 .BR \-O ", " \-\^\-only-files
250 Ignore all special files, except for symlinks. Yet, when recursing
251 into directories, ignore symlinked directories as well.
253 .BR \-s ", " \-\^\-no-messages
254 Suppress error messages about nonexistent or unreadable files.
255 Portability note: unlike \s-1GNU\s0
259 did not conform to \s-1POSIX.2\s0, because traditional
265 option behaved like \s-1GNU\s0
269 Shell scripts intended to be portable to traditional
275 and should redirect output to /dev/null instead.
277 .BR \-U ", " \-\^\-binary
278 Treat the file(s) as binary. By default, under MS-DOS and MS-Windows,
280 guesses the file type by looking at the contents of the first 32KB
281 read from the file. If
283 decides the file is a text file, it strips the CR characters from the
284 original file contents (to make regular expressions with
288 work correctly). Specifying
290 overrules this guesswork, causing all files to be read and passed to the
291 matching mechanism verbatim; if the file is a text file with CR/LF
292 pairs at the end of each line, this will cause some regular
294 This option has no effect on platforms other than MS-DOS and
297 .BR \-u ", " \-\^\-unix-byte-offsets
298 Report Unix-style byte offsets. This switch causes
300 to report byte offsets as if the file were Unix-style text file, i.e. with
301 CR characters stripped off. This will produce results identical to running
303 on a Unix machine. This option has no effect unless
306 it has no effect on platforms other than MS-DOS and MS-Windows.
308 .BR \-V ", " \-\^\-version
309 Print the version number of
311 to standard error. This version number should
312 be included in all bug reports (see below).
314 .BR \-v ", " \-\^\-invert-match
315 Invert the sense of matching, to select non-matching lines.
317 .BR \-w ", " \-\^\-word-regexp
318 Select only those lines containing matches that form whole words.
319 The test is that the matching substring must either be at the
320 beginning of the line, or preceded by a non-word constituent
321 character. Similarly, it must be either at the end of the line
322 or followed by a non-word constituent character. Word-constituent
323 characters are letters, digits, and the underscore.
325 .BR \-x ", " \-\^\-line-regexp
326 Select only those matches that exactly match the whole line.
333 Output a zero byte (the \s-1ASCII\s0
335 character) instead of the character that normally follows a file name.
337 .B "grep \-l \-\^\-null"
338 outputs a zero byte after each file name instead of the usual newline.
339 This option makes the output unambiguous, even in the presence of file
340 names containing unusual characters like newlines. This option can be
341 used with commands like
342 .BR "find \-print0" ,
347 to process arbitrary file names,
348 even those that contain newline characters.
350 .BR \-Z ", " \-\^\-decompress
351 Decompress the input data before searching.
352 This option is only available if compiled with zlib(3) library.
353 .SH "REGULAR EXPRESSIONS"
354 A regular expression is a pattern that describes a set of strings.
355 Regular expressions are constructed analogously to arithmetic
356 expressions, by using various operators to combine smaller expressions.
359 understands two different versions of regular expression syntax:
360 \*(lqbasic\*(rq and \*(lqextended.\*(rq In
361 .RB "\s-1GNU\s0\ " grep ,
362 there is no difference in available functionality using either syntax.
363 In other implementations, basic regular expressions are less powerful.
364 The following description applies to extended regular expressions;
365 differences for basic regular expressions are summarized afterwards.
367 The fundamental building blocks are the regular expressions that match
368 a single character. Most characters, including all letters and digits,
369 are regular expressions that match themselves. Any metacharacter with
370 special meaning may be quoted by preceding it with a backslash.
372 A list of characters enclosed by
377 character in that list; if the first character of the list
380 then it matches any character
383 For example, the regular expression
385 matches any single digit. A range of characters
386 may be specified by giving the first and last characters, separated
388 Finally, certain named classes of characters are predefined.
389 Their names are self explanatory, and they are
406 except the latter form depends upon the \s-1POSIX\s0 locale and the
407 \s-1ASCII\s0 character encoding, whereas the former is independent
408 of locale and character set.
409 (Note that the brackets in these class names are part of the symbolic
410 names, and must be included in addition to the brackets delimiting
411 the bracket list.) Most metacharacters lose their special meaning
412 inside lists. To include a literal
414 place it first in the list. Similarly, to include a literal
416 place it anywhere but first. Finally, to include a literal
422 matches any single character.
436 are metacharacters that respectively match the empty string at the
437 beginning and end of a line.
442 respectively match the empty string at the beginning and end of a word.
445 matches the empty string at the edge of a word,
448 matches the empty string provided it's
450 at the edge of a word.
452 A regular expression may be followed by one of several repetition operators:
456 The preceding item is optional and matched at most once.
459 The preceding item will be matched zero or more times.
462 The preceding item will be matched one or more times.
465 The preceding item is matched exactly
470 The preceding item is matched
475 The preceding item is matched at least
477 times, but not more than
482 Two regular expressions may be concatenated; the resulting
483 regular expression matches any string formed by concatenating
484 two substrings that respectively match the concatenated
487 Two regular expressions may be joined by the infix operator
489 the resulting regular expression matches any string matching
490 either subexpression.
492 Repetition takes precedence over concatenation, which in turn
493 takes precedence over alternation. A whole subexpression may be
494 enclosed in parentheses to override these precedence rules.
500 is a single digit, matches the substring
501 previously matched by the
503 parenthesized subexpression of the regular expression.
505 In basic regular expressions the metacharacters
513 lose their special meaning; instead use the backslashed
527 metacharacter, and some
529 implementations support
531 instead, so portable scripts should avoid
535 patterns and should use
542 attempts to support traditional usage by assuming that
544 is not special if it would be the start of an invalid interval
545 specification. For example, the shell command
547 searches for the two-character string
549 instead of reporting a syntax error in the regular expression.
550 \s-1POSIX.2\s0 allows this behavior as an extension, but portable scripts
552 .SH "ENVIRONMENT VARIABLES"
555 This variable specifies default options to be placed in front of any
556 explicit options. For example, if
559 .BR "'\-\^\-binary-files=without-match \-\^\-directories=skip'" ,
561 behaves as if the two options
562 .B \-\^\-binary-files=without-match
564 .B \-\^\-directories=skip
565 had been specified before any explicit options.
566 Option specifications are separated by whitespace.
567 A backslash escapes the next character,
568 so it can be used to specify an option containing whitespace or a backslash.
570 \fBLC_ALL\fP, \fBLC_MESSAGES\fP, \fBLANG\fP
571 These variables specify the
573 locale, which determines the language that
576 The locale is determined by the first of these variables that is set.
577 American English is used if none of these environment variables are set,
578 or if the message catalog is not installed, or if
580 was not compiled with national language support (\s-1NLS\s0).
582 \fBLC_ALL\fP, \fBLC_CTYPE\fP, \fBLANG\fP
583 These variables specify the
585 locale, which determines the type of characters, e.g., which
586 characters are whitespace.
587 The locale is determined by the first of these variables that is set.
588 The \s-1POSIX\s0 locale is used if none of these environment variables
589 are set, or if the locale catalog is not installed, or if
591 was not compiled with national language support (\s-1NLS\s0).
596 behaves as \s-1POSIX.2\s0 requires; otherwise,
598 behaves more like other \s-1GNU\s0 programs.
599 \s-1POSIX.2\s0 requires that options that follow file names must be
600 treated as file names; by default, such options are permuted to the
601 front of the operand list and are treated as options.
602 Also, \s-1POSIX.2\s0 requires that unrecognized options be diagnosed as
603 \*(lqillegal\*(rq, but since they are not really against the law the default
604 is to diagnose them as \*(lqinvalid\*(rq.
606 Normally, exit status is 0 if matches were found,
607 and 1 if no matches were found. (The
609 option inverts the sense of the exit status.)
610 Exit status is 2 if there were syntax errors
611 in the pattern, inaccessible input files, or
615 .BR bug-gnu-utils@gnu.org .
616 Be sure to include the word \*(lqgrep\*(rq somewhere in the
617 \*(lqSubject:\*(rq field.
619 Large repetition counts in the
621 construct may cause grep to use lots of memory.
623 certain other obscure regular expressions require exponential time
624 and space, and may cause
626 to run out of memory.
628 Backreferences are very slow, and may require exponential time.
629 .\" Work around problems with some troff -man implementations.