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

FreeBSD Manual Pages

  
 
  

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

NAME
       grep,  egrep,  fgrep, zgrep, zegrep, zfgrep, bzgrep, bzegrep, bzfgrep -
       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.  zgrep	is the
       same as grep -Z.	 zegrep	is the same as grep -EZ.  zfgrep is  the  same
       as grep -FZ.

OPTIONS
       -A NUM, --after-context=NUM
	      Print NUM	lines of trailing context after	matching lines.

       -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.

       -C [NUM], -NUM, --context[=NUM]
	      Print NUM	lines (default 2) of output context.

       -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.

       -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, --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.

       -f FILE,	--file=FILE
	      Obtain patterns from FILE, one per line.	The  empty  file  con-
	      tains zero patterns, and therfore	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.

       --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.

       -q, --quiet, --silent
	      Quiet; suppress normal output.  The scanning will	 stop  on  the
	      first match.  Also see the -s or --no-messages option below.

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

       -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.

       --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.

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 list of characters enclosed by	[ and ]	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  ex-
       pression	 [0123456789] matches any single digit.	 A range of characters
       may be specified	by giving the first and	last characters, separated  by
       a hyphen.  Finally, certain named classes of characters are predefined.
       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 depends upon the POSIX locale and
       the ASCII character encoding, whereas the former	is independent of  lo-
       cale  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  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_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.

       LC_ALL, LC_MESSAGES, LANG
	      These variables specify the LC_MESSAGES locale, which determines
	      the  language that grep uses for messages.  The locale is	deter-
	      mined by the first of these variables  that  is  set.   American
	      English  is used if none of these	environment variables are set,
	      or if the	message	catalog	is not installed, or if	grep  was  not
	      compiled with national language support (NLS).

       LC_ALL, LC_CTYPE, LANG
	      These  variables	specify	 the LC_CTYPE locale, which determines
	      the type of characters, e.g., which characters  are  whitespace.
	      The locale is determined by the first of these variables that is
	      set.  The	POSIX locale is	used  if  none	of  these  environment
	      variables	are set, or if the locale catalog is not installed, or
	      if grep was not compiled with national language support (NLS).

       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".

DIAGNOSTICS
       Normally,  exit	status is 0 if matches were found, and 1 if no matches
       were found.  (The -v option inverts the	sense  of  the	exit  status.)
       Exit status is 2	if there were syntax errors in the pattern, inaccessi-
       ble input files,	or other system	errors.

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 {m,n} 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			  2000/01/26			       GREP(1)

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

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=egrep&sektion=1&manpath=FreeBSD+5.2-RELEASE+and+Ports>

home | help