GREP(1) OpenBSD Reference Manual GREP(1)NAME
grep, egrep, fgrep, zgrep, zegrep, zfgrep - file pattern searcher
SYNOPSIS
grep [-abcEFGhIiLlnqRsUVvwxZ] [-A num] [-B num] [-C[num]] [-e pattern]
[-f file] [--binary-files=value] [--context[=num]] [--line-buffered]
[pattern] [file ...]
DESCRIPTION
The grep utility searches any given input files, selecting lines that
match one or more patterns. By default, a pattern matches an input line
if the regular expression (RE) in the pattern matches the input line
without its trailing newline. An empty expression matches every line.
Each input line that matches at least one of the patterns is written to
the standard output. If no file arguments are specified, the standard
input is used.
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.
zgrep, zegrep, and zfgrep act like grep, egrep, and fgrep, respectively,
but accept input files compressed with the compress(1) or gzip(1)
compression utilities.
The following options are available:
-A num Print num lines of trailing context after each match. See also
the -B and -C options.
-a 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 Print num lines of leading context before each match. See also
the -A and -C options.
-b The offset in bytes of a matched pattern is displayed in front of
the respective matched line.
-C[num]
Print num lines of leading and trailing context surrounding each
match. The default is 2 and is equivalent to -A 2 -B 2. Note:
no whitespace may be given between the option and its argument.
-c Only a count of selected lines is written to standard output.
-E Interpret pattern as an extended regular expression (i.e. force
grep to behave as egrep).
-e 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
(`-').
-F Interpret pattern as a set of fixed strings (i.e. force grep to
behave as fgrep).
-f 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 Interpret pattern as a basic regular expression (i.e. force grep
to behave as traditional grep).
-h Never print filename headers (i.e. filenames) with output lines.
-I Ignore binary files.
-i Perform case insensitive matching. By default, grep is case
sensitive.
-L 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.
-l 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.
-n 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.
-q Quiet mode: suppress normal output. grep will only search a file
until a match has been found, making searches potentially less
expensive.
-R Recursively search subdirectories listed.
-s Silent mode. Nonexistent and unreadable files are ignored (i.e.
their error messages are suppressed).
-U Search binary files, but do not attempt to print them.
-V Display version information. All other options are ignored.
-v Selected lines are those not matching any of the specified
patterns.
-w The expression is searched for as a word (as if surrounded by
`[[:<:]]' and `[[:>:]]'; see re_format(7)).
-x Only input lines selected against an entire fixed string or
regular expression are considered to be matching lines.
-Z Force grep to behave as zgrep.
--binary-files=value
Controls searching and printing of binary files. Options are
binary, the default: search binary files but do not print them;
without-match: do not search binary files; and text: treat all
files as text.
--context[=num]
Print num lines of leading and trailing context. The default is
2.
--line-buffered
Force output to be line buffered. By default, output is line
buffered when standard output is a terminal and block buffered
otherwise.
EXIT STATUS
The grep utility exits with one of the following values:
0 One or more lines were selected.
1 No lines were selected.
>1 An error occurred.
EXAMPLES
To find all occurrences of the word `patricia' in a file:
$ grep 'patricia' myfile
To find all occurrences of the pattern `.Pp' at the beginning of a line:
$ grep '^\.Pp' myfile
The apostrophes ensure the entire expression is evaluated by grep instead
of by the user's shell. The caret `^' matches the null string at the
beginning of a line, and the `\' escapes the `.', which would otherwise
match any character.
To find all lines in a file which do not contain the words `foo' or
`bar':
$ grep -v -e 'foo' -e 'bar' myfile
A simple example of an extended regular expression:
$ egrep '19|20|25' calendar
Peruses the file `calendar' looking for either 19, 20, or 25.
SEE ALSOed(1), ex(1), gzip(1), sed(1), re_format(7)STANDARDS
The grep utility is compliant with the IEEE Std 1003.1-2008 (``POSIX'')
specification.
The flags [-AaBbCGhILRUVwZ] are extensions to that specification, and the
behaviour of the -f flag when used with an empty pattern file is left
undefined.
All long options are provided for compatibility with GNU versions of this
utility.
Historic versions of the grep utility also supported the flags [-ruy].
This implementation supports those options; however, their use is
strongly discouraged.
HISTORY
The grep command first appeared in Version 6 AT&T UNIX.
OpenBSD 4.9 September 3, 2010 OpenBSD 4.9
