grep(1) General Commands Manual grep(1)
NAME
grep, egrep, fgrep - search a file for a pattern
SYNOPSIS
Plain call with pattern
pattern [file ...]
Call with (multiple) -e pattern
pattern] ... [file ...]
Call with -f file
pattern_file] [file ...]
Obsolescent:
[expression] [file ...]
[strings] [file ...]
DESCRIPTION
The command searches the input text files (standard input default) for lines matching a pattern. Normally, each line found is copied to
the standard output. supports the Basic Regular Expression syntax (see regexp(5)). The option supports Extended Regular Expression (ERE)
syntax (see regexp(5)). The option searches for fixed strings using the fast Boyer-Moore string searching algorithm. The and options
treat newlines embedded in the pattern as alternation characters. A null expression or string matches every line.
The forms and are maintained for backward compatibility. The use of the and options is recommended for portability.
Options
Extended regular expressions.
Each pattern specified is a sequence of one or more EREs. The EREs can be separated by newline characters or
given in separate expression options. A pattern matches an input line if any ERE in the sequence matches the
contents of the input line without its trailing newline character. The same functionality is obtained by using
Fixed strings. Each pattern specified is a sequence of one or more strings. Strings can be separated by newline characters or
given in separate expression options. A pattern matches an input line if the line contains any of the strings
in the sequence. The same functionality is obtained by using
Each line is preceded by the block number on which it was found.
This is useful in locating disk block numbers by context. Block numbers are calculated by dividing by 512 the
number of bytes that have been read from the file and rounding down the result.
Only a count of matching lines is printed.
Same as a simple expression argument, but useful when the expression begins with a hyphen Multiple options can be used to specify
multiple patterns; an input line is selected if it matches any of the specified patterns.
The regular expression and or strings list is taken from the pattern_file.
Suppress printing of filenames when searching multiple files.
Ignore uppercase/lowercase distinctions during comparisons.
Only the names of files with matching lines are listed (once),
separated by newlines. If standard input is searched, a path name of will be written, in the POSIX locale. In
other locales, may be replaced by something more appropriate in those locales.
Each line is preceded by its relative line number in the file starting at 1.
The line number is reset for each file searched. This option is ignored if or is specified.
(Quiet) Do not write anything to the standard output, regardless of matching lines. Exit with zero status upon finding
the first matching line. Overrides any options that would produce output.
Error messages produced for nonexistent or unreadable files are suppressed.
All lines but those matching are printed.
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 pre-
ceded by a non-word constituent 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.
(eXact) Matches are recognized only when the entire input line matches the fixed string or regular expression.
The file name is output in all the cases in which output is generated if there are more than one input file, unless the -h option is speci-
fied. Care should be taken when using the characters and in expression, because they are also meaningful to the shell. It is safest to
enclose the entire expression argument in single quotes
EXTERNAL INFLUENCES
Environment Variables
determines the locale to use for the locale categories when both and the corresponding environment variable (beginning with do not specify
a locale. If is not specified or is set to the empty string, a default of (see lang(5)) is used.
determines the locale to use to override any values for locale categories specified by the settings of or any environment variables begin-
ning with
determines the collating sequence used in evaluating regular expressions.
determines the interpretation of text as single byte and/or multi-byte characters, the classification of characters as letters, the case
information for the option, and the characters matched by character class expressions in regular expressions.
determines the language in which messages are displayed.
If any internationalization variable contains an invalid setting, the commands behave as if all internationalization variables are set to
See environ(5).
International Code Set Support
Single-byte and multi-byte character code sets are supported.
RETURN VALUE
Upon completion, returns one of the following values:
One or more matches found.
No match found.
Syntax error or inaccessible file (even if matches were found).
EXAMPLES
In the POSIX shell (sh(1)) the following example searches two files, finding all lines containing occurrences of any of four strings:
Note that the single quotes are necessary to tell when the strings have ended and the file names have begun.
For the C shell (see csh(1)) the following command can be used:
To search a file named containing the following entries:
the command:
prints:
To search a file for lines that contain either a or use either of the following commands:
Search all files in the current directory for the string
Search all files in the current directory subtree for the string and ensure that no error occurs due to file name expansion exceeding sys-
tem argument list limits:
The previous example does not print the name of files where string appears. To force to print file names, add a second argument to the
command portion of the command line:
In this form, the first file name is that produced by and the second file name is the null file.
WARNINGS
(XPG4 only.) If the option is specified, the exit status will be zero if an input line is selected, even if an error was detected. Other-
wise, default actions will be performed.
If the option is specified with non-word constituent characters, then the output is unexpected.
SEE ALSO
sed(1), sh(1), regcomp(3C), environ(5), lang(5), regexp(5).
STANDARDS CONFORMANCE
grep(1)