Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
GREP(1)			    General Commands Manual		       GREP(1)

       grep,  egrep,  fgrep, zgrep, zegrep, zfgrep, bzgrep, bzegrep, bzfgrep -
       print lines matching a pattern

       grep [options] PATTERN [FILE...]
       grep [options] [-e PATTERN | -f FILE] [FILE...]

       grep searches the named input FILEs (or standard	input if no files  are
       named, or the file name - is given) for lines containing	a match	to the
       given PATTERN.  By default, grep	prints the matching lines.

       In addition, two	variant	programs egrep and fgrep are available.	 egrep
       is  the	same  as grep -E.  fgrep is the	same as	grep -F.  zgrep	is the
       same as grep -Z.	 zegrep	is the same as grep -EZ.  zfgrep is  the  same
       as grep -FZ.

       -A NUM, --after-context=NUM
	      Print  NUM  lines	 of  trailing  context	after  matching	lines.
	      Places  a	 line  containing  --  between	contiguous  groups  of

       -a, --text
	      Process  a binary	file as	if it were text; this is equivalent to
	      the --binary-files=text option.

       -B NUM, --before-context=NUM
	      Print NUM	 lines	of  leading  context  before  matching	lines.
	      Places  a	 line  containing  --  between	contiguous  groups  of

       -C NUM, --context=NUM
	      Print NUM	lines of output	context.  Places a line	containing  --
	      between contiguous groups	of matches.

       -b, --byte-offset
	      Print  the byte offset within the	input file before each line of

	      If the first few bytes of	a file indicate	that the file contains
	      binary  data, assume that	the file is of type TYPE.  By default,
	      TYPE is binary, and grep normally	outputs	either a one-line mes-
	      sage  saying  that a binary file matches,	or no message if there
	      is no match.  If TYPE is without-match, grep assumes that	a  bi-
	      nary  file  does not match; this is equivalent to	the -I option.
	      If TYPE is text, grep processes a	binary	file  as  if  it  were
	      text;  this is equivalent	to the -a option.  Warning: grep --bi-
	      nary-files=text might output  binary  garbage,  which  can  have
	      nasty side effects if the	output is a terminal and if the	termi-
	      nal driver interprets some of it as commands.

       --colour[=WHEN],	--color[=WHEN]
	      Surround the matching string with	the marker find	in  GREP_COLOR
	      environment variable. WHEN may be	`never', `always', or `auto'

       -c, --count
	      Suppress	normal output; instead print a count of	matching lines
	      for each input file.  With the -v,  --invert-match  option  (see
	      below), count non-matching lines.

       -D ACTION, --devices=ACTION
	      If  an  input  file  is  a device, FIFO or socket, use ACTION to
	      process it.  By default, ACTION is read, which  means  that  de-
	      vices  are  read just as if they were ordinary files.  If	ACTION
	      is skip, devices are silently skipped.

       -d ACTION, --directories=ACTION
	      If an input file is a directory, use ACTION to process  it.   By
	      default,	ACTION	is read, which means that directories are read
	      just as if they were ordinary files.  If ACTION is skip,	direc-
	      tories  are  silently skipped.  If ACTION	is recurse, grep reads
	      all files	under each directory, recursively; this	is  equivalent
	      to the -r	option.

       -E, --extended-regexp
	      Interpret	PATTERN	as an extended regular expression (see below).

       -e PATTERN, --regexp=PATTERN
	      Use PATTERN as the pattern; useful to protect patterns beginning
	      with -.

       -F, --fixed-strings
	      Interpret	PATTERN	as a list of fixed strings, separated by  new-
	      lines, any of which is to	be matched.

       -P, --perl-regexp
	      Interpret	PATTERN	as a Perl regular expression.

       -f FILE,	--file=FILE
	      Obtain  patterns	from  FILE, one	per line.  The empty file con-
	      tains zero patterns, and therefore matches nothing.

       -G, --basic-regexp
	      Interpret	PATTERN	as a basic  regular  expression	 (see  below).
	      This is the default.

       -H, --with-filename
	      Print the	filename for each match.

       -h, --no-filename
	      Suppress	the  prefixing	of  filenames  on output when multiple
	      files are	searched.

       --help Output a brief help message.

       -I     Process a	binary file as if it did not  contain  matching	 data;
	      this is equivalent to the	--binary-files=without-match option.

       -i, --ignore-case
	      Ignore  case  distinctions  in  both  the	 PATTERN and the input

       -L, --files-without-match
	      Suppress normal output; instead print the	 name  of  each	 input
	      file from	which no output	would normally have been printed.  The
	      scanning will stop on the	first match.

       -l, --files-with-matches
	      Suppress normal output; instead print the	 name  of  each	 input
	      file  from  which	 output	would normally have been printed.  The
	      scanning will stop on the	first match.

       -m NUM, --max-count=NUM
	      Stop reading a file after	NUM matching lines.  If	the  input  is
	      standard	input  from a regular file, and	NUM matching lines are
	      output, grep ensures that	the standard input  is	positioned  to
	      just  after the last matching line before	exiting, regardless of
	      the presence of trailing context lines.  This enables a  calling
	      process  to resume a search.  When grep stops after NUM matching
	      lines, it	outputs	any trailing context lines.  When  the	-c  or
	      --count  option  is  also	 used,	grep  does  not	output a count
	      greater than NUM.	 When the -v or	--invert-match option is  also
	      used, grep stops after outputting	NUM non-matching lines.

       --mmap If  possible, use	the mmap(2) system call	to read	input, instead
	      of the default read(2) system call.  In some situations,	--mmap
	      yields  better performance.  However, --mmap can cause undefined
	      behavior (including core dumps) if an input file	shrinks	 while
	      grep is operating, or if an I/O error occurs.

       -n, --line-number
	      Prefix each line of output with the line number within its input

       -o, --only-matching
	      Show only	the part of a matching line that matches PATTERN.

	      Displays input actually coming from standard input as input com-
	      ing  from	 file LABEL.  This is especially useful	for tools like
	      zgrep, e.g.  gzip	-cd foo.gz |grep --label=foo something

	      Flush output on every line.  Note	that this incurs a performance

       -q, --quiet, --silent
	      Quiet;  do  not write anything to	standard output.  Exit immedi-
	      ately with zero status if	any match is found, even if  an	 error
	      was detected.  Also see the -s or	--no-messages option.

       -R, -r, --recursive
	      Read all files under each	directory, recursively;	this is	equiv-
	      alent to the -d recurse option.

	      Recurse in directories only searching file matching PATTERN.

	      Recurse in directories skip file matching	PATTERN.

       -s, --no-messages
	      Suppress error messages about nonexistent	or  unreadable	files.
	      Portability note:	unlike GNU grep, traditional grep did not con-
	      form to POSIX.2, because traditional grep	lacked a -q option and
	      its  -s option behaved like GNU grep's -q	option.	 Shell scripts
	      intended to be portable to traditional grep should avoid both -q
	      and -s and should	redirect output	to /dev/null instead.

       -U, --binary
	      Treat  the  file(s) as binary.  By default, under	MS-DOS and MS-
	      Windows, grep guesses the	file type by looking at	 the  contents
	      of  the first 32KB read from the file.  If grep decides the file
	      is a text	file, it strips	the CR characters  from	 the  original
	      file  contents  (to  make	 regular expressions with ^ and	$ work
	      correctly).  Specifying -U overrules this	guesswork, causing all
	      files  to	be read	and passed to the matching mechanism verbatim;
	      if the file is a text file with CR/LF pairs at the end  of  each
	      line,  this  will	 cause some regular expressions	to fail.  This
	      option has no effect on platforms	other than MS-DOS and  MS-Win-

       -u, --unix-byte-offsets
	      Report  Unix-style byte offsets.	This switch causes grep	to re-
	      port byte	offsets	as if the file were Unix-style text file, i.e.
	      with  CR	characters  stripped  off.   This will produce results
	      identical	to running grep	on a Unix machine.  This option	has no
	      effect  unless -b	option is also used; it	has no effect on plat-
	      forms other than MS-DOS and MS-Windows.

       -V, --version
	      Print the	version	number of grep to standard error.   This  ver-
	      sion number should be included in	all bug	reports	(see below).

       -v, --invert-match
	      Invert the sense of matching, to select non-matching lines.

       -w, --word-regexp
	      Select  only  those  lines  containing  matches  that form whole
	      words.  The test is that the matching substring must  either  be
	      at  the  beginning  of  the line,	or preceded by a non-word con-
	      stituent character.  Similarly, it must be either	at the end  of
	      the line or followed by a	non-word constituent character.	 Word-
	      constituent characters are letters, digits, and the underscore.

       -x, --line-regexp
	      Select only those	matches	that exactly match the whole line.

       -y     Obsolete synonym for -i.

       --null Output a zero byte (the ASCII  NUL  character)  instead  of  the
	      character	 that normally follows a file name.  For example, grep
	      -l --null	outputs	a zero byte after each file  name  instead  of
	      the  usual  newline.   This option makes the output unambiguous,
	      even in the presence of file names containing unusual characters
	      like  newlines.  This option can be used with commands like find
	      -print0, perl -0,	sort -z, and xargs  -0	to  process  arbitrary
	      file names, even those that contain newline characters.

       -Z, --decompress
	      Decompress the input data	before searching.  This	option is only
	      available	if compiled with zlib(3) library.

       -J, --bz2decompress
	      Decompress the bzip2(1) compressed input data before searching.

       A regular expression is a pattern that  describes  a  set  of  strings.
       Regular	expressions  are constructed analogously to arithmetic expres-
       sions, by using various operators to combine smaller expressions.

       grep understands	two different versions of regular  expression  syntax:
       "basic"	and "extended."	 In GNU	grep, there is no difference in	avail-
       able functionality using	either syntax.	In other implementations,  ba-
       sic  regular  expressions are less powerful.  The following description
       applies to extended regular expressions;	differences for	basic  regular
       expressions are summarized afterwards.

       The  fundamental	building blocks	are the	regular	expressions that match
       a single	character.  Most characters, including all letters and digits,
       are  regular expressions	that match themselves.	Any metacharacter with
       special meaning may be quoted by	preceding it with a backslash.

       A bracket expression is a list of characters enclosed by	[ and  ].   It
       matches	any  single  character in that list; if	the first character of
       the list	is the caret ^ then it matches any character not in the	 list.
       For  example,  the  regular  expression [0123456789] matches any	single

       Within a	bracket	expression, a range expression consists	of two charac-
       ters separated by a hyphen.  It matches any single character that sorts
       between the two characters, inclusive, using the	locale's collating se-
       quence  and character set.  For example,	in the default C locale, [a-d]
       is equivalent to	[abcd].	 Many locales sort  characters	in  dictionary
       order,  and  in	these  locales	[a-d]  is  typically not equivalent to
       [abcd]; it might	be equivalent to [aBbCcDd], for	 example.   To	obtain
       the  traditional	interpretation of bracket expressions, you can use the
       C locale	by setting the LC_ALL environment variable to the value	C.

       Finally,	certain	named classes  of  characters  are  predefined	within
       bracket expressions, as follows.	 Their names are self explanatory, and
       they  are  [:alnum:],  [:alpha:],  [:blank:],   [:cntrl:],   [:digit:],
       [:graph:],  [:lower:],  [:print:], [:punct:], [:space:],	[:upper:], and
       [:xdigit:].  For	example, [[:alnum:]]  means  [0-9A-Za-z],  except  the
       latter form depends upon	the C locale and the ASCII character encoding,
       whereas the former is independent of locale and character  set.	 (Note
       that  the brackets in these class names are part	of the symbolic	names,
       and must	be included in addition	to the brackets	delimiting the bracket
       list.)	Most  metacharacters  lose their special meaning inside	lists.
       To include a literal ] place it first in	the list.  Similarly,  to  in-
       clude  a	 literal ^ place it anywhere but first.	 Finally, to include a
       literal - place it last.

       The period .  matches any single	character.  The	symbol \w is a synonym
       for [[:alnum:]] and \W is a synonym for [^[:alnum:]].

       The  caret ^ and	the dollar sign	$ are metacharacters that respectively
       match the empty string at the beginning and end of a line.  The symbols
       \<  and \> respectively match the empty string at the beginning and end
       of a word.  The symbol \b matches the empty string at  the  edge	 of  a
       word,  and \B matches the empty string provided it's not	at the edge of
       a word.

       A regular expression may	be followed by one of several repetition oper-
       ?      The preceding item is optional and matched at most once.
       *      The preceding item will be matched zero or more times.
       +      The preceding item will be matched one or	more times.
       {n}    The preceding item is matched exactly n times.
       {n,}   The preceding item is matched n or more times.
       {n,m}  The  preceding  item  is	matched	at least n times, but not more
	      than m times.

       Two regular expressions may be concatenated; the	resulting regular  ex-
       pression	matches	any string formed by concatenating two substrings that
       respectively match the concatenated subexpressions.

       Two regular expressions may be joined by	the infix operator |; the  re-
       sulting	regular	 expression  matches any string	matching either	subex-

       Repetition takes	precedence over	concatenation,	which  in  turn	 takes
       precedence  over	alternation.  A	whole subexpression may	be enclosed in
       parentheses to override these precedence	rules.

       The backreference \n, where n is	a single digit,	matches	the  substring
       previously  matched by the nth parenthesized subexpression of the regu-
       lar expression.

       In basic	regular	expressions the	metacharacters ?, +, {,	|,  (,	and  )
       lose  their  special  meaning; instead use the backslashed versions \?,
       \+, \{, \|, \(, and \).

       Traditional egrep did not support the { metacharacter, and  some	 egrep
       implementations	support	\{ instead, so portable	scripts	should avoid {
       in egrep	patterns and should use	[{] to match a literal {.

       GNU egrep attempts to support traditional usage by assuming that	 {  is
       not  special if it would	be the start of	an invalid interval specifica-
       tion.  For example, the shell command egrep '{1'	searches for the  two-
       character  string {1 instead of reporting a syntax error	in the regular
       expression.  POSIX.2 allows this	behavior as an extension, but portable
       scripts should avoid it.

       Grep's behavior is affected by the following environment	variables.

       A  locale  LC_foo is specified by examining the three environment vari-
       ables LC_ALL, LC_foo, LANG, in that order.  The first  of  these	 vari-
       ables  that is set specifies the	locale.	 For example, if LC_ALL	is not
       set, but	LC_MESSAGES is set to pt_BR, then Brazilian Portuguese is used
       for  the	LC_MESSAGES locale.  The C locale is used if none of these en-
       vironment variables are set, or if the locale catalog is	not installed,
       or if grep was not compiled with	national language support (NLS).

	      This variable specifies default options to be placed in front of
	      any explicit options.  For example, if  GREP_OPTIONS  is	'--bi-
	      nary-files=without-match --directories=skip', grep behaves as if
	      the  two	options	 --binary-files=without-match  and  --directo-
	      ries=skip	 had  been specified before any	explicit options.  Op-
	      tion specifications are separated	by  whitespace.	  A  backslash
	      escapes  the next	character, so it can be	used to	specify	an op-
	      tion containing whitespace or a backslash.

	      Specifies	the marker for highlighting.

	      These variables specify the LC_COLLATE locale, which  determines
	      the  collating sequence used to interpret	range expressions like

	      These variables specify the LC_CTYPE  locale,  which  determines
	      the type of characters, e.g., which characters are whitespace.

	      These variables specify the LC_MESSAGES locale, which determines
	      the language that	grep uses for messages.	 The default C	locale
	      uses American English messages.

	      If  set,	grep  behaves as POSIX.2 requires; otherwise, grep be-
	      haves more like other GNU	programs.  POSIX.2 requires  that  op-
	      tions  that  follow file names must be treated as	file names; by
	      default, such options are	permuted to the	front of  the  operand
	      list  and	 are  treated as options.  Also, POSIX.2 requires that
	      unrecognized options be diagnosed	as "illegal", but  since  they
	      are  not	really against the law the default is to diagnose them
	      as "invalid".

       Normally, exit status is	0 if selected lines are	found and 1 otherwise.
       But the exit status is 2	if an error occurred, unless the -q or --quiet
       or --silent option is used and a	selected line is found.

       Email bug reports to  Be	sure  to  include  the
       word "grep" somewhere in	the "Subject:" field.

       Large  repetition  counts  in the {n,m} construct may cause grep	to use
       lots of memory.	In addition, certain other obscure regular expressions
       require	exponential  time  and space, and may cause grep to run	out of

       Backreferences are very slow, and may require exponential time.

GNU Project			  2002/01/22			       GREP(1)


Want to link to this manual page? Use this URL:

home | help