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GREP(1)			    General Commands Manual		       GREP(1)

NAME
       grep, egrep, fgrep - print lines	matching a pattern

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

DESCRIPTION
       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.

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

       -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
	      matches.

       -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
	      output.

       --binary-files=TYPE
	      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	Inter-
	      pret 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
	      files.

       -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
	      file.

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

       --label=LABEL
	      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

       --line-buffering
	      Use line buffering, it can be a performance penality.

       -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.

	 --include=PATTERN
	      Recurse in directories only searching file matching PATTERN.

	 --exclude=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-
	      dows.

       -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.

       -Z, --null
	      Output  a	 zero  byte  (the  ASCII NUL character)	instead	of the
	      character	that normally follows a	file name.  For	example,  grep
	      -lZ  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.

REGULAR	EXPRESSIONS
       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
       digit.

       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:],  [:cntrl:],   [:digit:],   [:graph:],
       [:lower:],  [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:].
       For example, [[:alnum:]]	means [0-9A-Za-z], except the latter form  de-
       pends  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 in-
       clude a literal ] place it first	in the list.  Similarly, to include  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-
       ators:
       ?      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-
       pression.

       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.

ENVIRONMENT VARIABLES
       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).

       GREP_OPTIONS
	      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.

       GREP_COLOR
	      Specifies	the marker for highlighting.

       LC_ALL, LC_COLLATE, LANG
	      These variables specify the LC_COLLATE locale, which  determines
	      the  collating sequence used to interpret	range expressions like
	      [a-z].

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

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

       POSIXLY_CORRECT
	      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".   POSIXLY_CORRECT	also  disables	 _N_GNU_nonop-
	      tion_argv_flags_,	described below.

       _N_GNU_nonoption_argv_flags_
	      (Here  N is grep's numeric process ID.)  If the ith character of
	      this environment variable's value	is 1, do not consider the  ith
	      operand  of  grep	to be an option, even if it appears to be one.
	      A	shell can put this variable in the environment for  each  com-
	      mand  it runs, specifying	which operands are the results of file
	      name wildcard expansion and therefore should not be  treated  as
	      options.	 This  behavior	 is  available only with the GNU C li-
	      brary, and only when POSIXLY_CORRECT is not set.

DIAGNOSTICS
       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.

BUGS
       Email bug reports to bug-gnu-utils@gnu.org.  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
       memory.

       Backreferences are very slow, and may require exponential time.

GNU Project			  2002/01/22			       GREP(1)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | REGULAR EXPRESSIONS | ENVIRONMENT VARIABLES | DIAGNOSTICS | BUGS

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