Manual Pages  — GREP

grep is used for simple patterns and basic regular expressions (BREs); egrep can handle extended regular expressions (EREs). See re_format(7) for more information on regular expressions. fgrep is quicker than both grep and egrep, but can only handle fixed patterns (i.e., it does not interpret regular expressions). Patterns may consist of one or more lines, allowing any of the pattern lines to match a portion of the input.

The following options are available:

-A num , -after-context= num
	Print num lines of trailing context after each match. See also the -B and -C options.
-a -, -text
	Treat all files as ASCII text. Normally grep will simply print "Binary file ... matches" if files contain binary characters. Use of this option forces grep to output lines matching the specified pattern.
-B num , -before-context= num
	Print num lines of leading context before each match. See also the -A and -C options.
-b -, -byte-offset
	The offset in bytes of a matched pattern is displayed in front of the respective matched line.
-C num , -context= num
	Print num lines of leading and trailing context surrounding each match. See also the -A and -B options.
-c -, -count
	Only a count of selected lines is written to standard output.
-colour= [when ], -color= [when ]
	Mark up the matching text with the expression stored in the GREP_COLOR environment variable. The possible values of when are " never", " always" and " auto".
-D action , -devices= action
	Specify the demanded action for devices, FIFOs and sockets. The default action is " read", which means, that they are read as if they were normal files. If the action is set to " skip", devices are silently skipped.
-d action , -directories= action
	Specify the demanded action for directories. It is " read" by default, which means that the directories are read in the same manner as normal files. Other possible values are " skip" to silently ignore the directories, and " recurse" to read them recursively, which has the same effect as the -R and -r option.
-E -, -extended-regexp
	Interpret pattern as an extended regular expression (i.e., force grep to behave as egrep).
-e pattern , -regexp= pattern
	Specify a pattern used during the search of the input: an input line is selected if it matches any of the specified patterns. This option is most useful when multiple -e options are used to specify multiple patterns, or when a pattern begins with a dash ('-').
-exclude pattern
	If specified, it excludes files matching the given filename pattern from the search. Note that -exclude and -include patterns are processed in the order given. If a name matches multiple patterns, the latest matching rule wins. If no -include pattern is specified, all files are searched that are not excluded. Patterns are matched to the full path specified, not only to the filename component.
-exclude-dir pattern
	If -R is specified, it excludes directories matching the given filename pattern from the search. Note that -exclude-dir and -include-dir patterns are processed in the order given. If a name matches multiple patterns, the latest matching rule wins. If no -include-dir pattern is specified, all directories are searched that are not excluded.
-F -, -fixed-strings
	Interpret pattern as a set of fixed strings (i.e., force grep to behave as fgrep).
-f file , -file= file
	Read one or more newline separated patterns from file. Empty pattern lines match every input line. Newlines are not considered part of a pattern. If file is empty, nothing is matched.
-G -, -basic-regexp
	Interpret pattern as a basic regular expression (i.e., force grep to behave as traditional grep).
-H
	Always print filename headers with output lines.
-h -, -no-filename
	Never print filename headers (i.e., filenames) with output lines.
-help
	Print a brief help message.
-I
	Ignore binary files. This option is equivalent to the "-binary-file= without-match" option.
-i -, -ignore-case
	Perform case insensitive matching. By default, grep is case sensitive.
-include pattern
	If specified, only files matching the given filename pattern are searched. Note that -include and -exclude patterns are processed in the order given. If a name matches multiple patterns, the latest matching rule wins. Patterns are matched to the full path specified, not only to the filename component.
-include-dir pattern
	If -R is specified, only directories matching the given filename pattern are searched. Note that -include-dir and -exclude-dir patterns are processed in the order given. If a name matches multiple patterns, the latest matching rule wins.
-L -, -files-without-match
	Only the names of files not containing selected lines are written to standard output. Pathnames are listed once per file searched. If the standard input is searched, the string "(standard input)" is written unless a -label is specified.
-l -, -files-with-matches
	Only the names of files containing selected lines are written to standard output. grep will only search a file until a match has been found, making searches potentially less expensive. Pathnames are listed once per file searched. If the standard input is searched, the string "(standard input)" is written unless a -label is specified.
-label
	Label to use in place of "(standard input)" for a file name where a file name would normally be printed. This option applies to -H, -L, and -l.
-mmap
	Use mmap(2) instead of read(2) to read input, which can result in better performance under some circumstances but can cause undefined behaviour.
-m num , -max-count= num
	Stop reading the file after num matches.
-n -, -line-number
	Each output line is preceded by its relative line number in the file, starting at line 1. The line number counter is reset for each file processed. This option is ignored if -c, -L, -l, or -q is specified.
-null
	Prints a zero-byte after the file name.
-O
	If -R is specified, follow symbolic links only if they were explicitly listed on the command line. The default is not to follow symbolic links.
-o -, -only-matching
	Prints only the matching part of the lines.
-p
	If -R is specified, no symbolic links are followed. This is the default.
-q -, -quiet -, -silent
	Quiet mode: suppress normal output. grep will only search a file until a match has been found, making searches potentially less expensive.
-R -, -r -, -recursive
	Recursively search subdirectories listed. (i.e., force grep to behave as rgrep).
-S
	If -R is specified, all symbolic links are followed. The default is not to follow symbolic links.
-s -, -no-messages
	Silent mode. Nonexistent and unreadable files are ignored (i.e., their error messages are suppressed).
-U -, -binary
	Search binary files, but do not attempt to print them.
-u
	This option has no effect and is provided only for compatibility with GNU grep.
-V -, -version
	Display version information and exit.
-v -, -invert-match
	Selected lines are those not matching any of the specified patterns.
-w -, -word-regexp
	The expression is searched for as a word (as if surrounded by '[[:<:]]' and '[[:>:]]'; see re_format(7)). This option has no effect if -x is also specified.
-x -, -line-regexp
	Only input lines selected against an entire fixed string or regular expression are considered to be matching lines.
-y
	Equivalent to -i. Obsoleted.
-z -, -null-data
	Treat input and output data as sequences of lines terminated by a zero-byte instead of a newline.
-binary-files= value
	Controls searching and printing of binary files. Options are:
binary (default)	Search binary files but do not print them.
without-match	Do not search binary files.
text	Treat all files as text.

-line-buffered	Force output to be line buffered. By default, output is line buffered when standard output is a terminal and block buffered otherwise.

If no file arguments are specified, the standard input is used. Additionally, " -" may be used in place of a file name, anywhere that a file name is accepted, to read from standard input. This includes both -f and file arguments.