|
PROLOG | NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OPERANDS | STDIN | INPUT FILES | ENVIRONMENT VARIABLES | ASYNCHRONOUS EVENTS | STDOUT | STDERR | OUTPUT FILES | EXTENDED DESCRIPTION | EXIT STATUS | CONSEQUENCES OF ERRORS | APPLICATION USAGE | EXAMPLES | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
GREP(1P) POSIX Programmer's Manual GREP(1P)
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
grep — search a file for a pattern
grep [−E|−F] [−c|−l|−q] [−insvx] −e pattern_list
[−e pattern_list]... [−f pattern_file]... [file...]
grep [−E|−F] [−c|−l|−q] [−insvx] [−e pattern_list]...
−f pattern_file [−f pattern_file]... [file...]
grep [−E|−F] [−c|−l|−q] [−insvx] pattern_list [file...]
The grep utility shall search the input files, selecting lines
matching one or more patterns; the types of patterns are controlled
by the options specified. The patterns are specified by the −e
option, −f option, or the pattern_list operand. The pattern_list's
value shall consist of one or more patterns separated by <newline>
characters; the pattern_file's contents shall consist of one or more
patterns terminated by a <newline> character. By default, an input
line shall be selected if any pattern, treated as an entire basic
regular expression (BRE) as described in the Base Definitions volume
of POSIX.1‐2008, Section 9.3, Basic Regular Expressions, matches any
part of the line excluding the terminating <newline>; a null BRE
shall match every line. By default, each selected input line shall be
written to the standard output.
Regular expression matching shall be based on text lines. Since a
<newline> separates or terminates patterns (see the −e and −f options
below), regular expressions cannot contain a <newline>. Similarly,
since patterns are matched against individual lines (excluding the
terminating <newline> characters) of the input, there is no way for a
pattern to match a <newline> found in the input.
The grep utility shall conform to the Base Definitions volume of
POSIX.1‐2008, Section 12.2, Utility Syntax Guidelines.
The following options shall be supported:
−E Match using extended regular expressions. Treat each
pattern specified as an ERE, as described in the Base
Definitions volume of POSIX.1‐2008, Section 9.4, Extended
Regular Expressions. If any entire ERE pattern matches
some part of an input line excluding the terminating
<newline>, the line shall be matched. A null ERE shall
match every line.
−F Match using fixed strings. Treat each pattern specified as
a string instead of a regular expression. If an input line
contains any of the patterns as a contiguous sequence of
bytes, the line shall be matched. A null string shall
match every line.
−c Write only a count of selected lines to standard output.
−e pattern_list
Specify one or more patterns to be used during the search
for input. The application shall ensure that patterns in
pattern_list are separated by a <newline>. A null pattern
can be specified by two adjacent <newline> characters in
pattern_list. Unless the −E or −F option is also
specified, each pattern shall be treated as a BRE, as
described in the Base Definitions volume of POSIX.1‐2008,
Section 9.3, Basic Regular Expressions. Multiple −e and −f
options shall be accepted by the grep utility. All of the
specified patterns shall be used when matching lines, but
the order of evaluation is unspecified.
−f pattern_file
Read one or more patterns from the file named by the
pathname pattern_file. Patterns in pattern_file shall be
terminated by a <newline>. A null pattern can be specified
by an empty line in pattern_file. Unless the −E or −F
option is also specified, each pattern shall be treated as
a BRE, as described in the Base Definitions volume of
POSIX.1‐2008, Section 9.3, Basic Regular Expressions.
−i Perform pattern matching in searches without regard to
case; see the Base Definitions volume of POSIX.1‐2008,
Section 9.2, Regular Expression General Requirements.
−l (The letter ell.) Write only the names of files containing
selected lines to standard output. Pathnames shall be
written once per file searched. If the standard input is
searched, a pathname of "(standardinput)" shall be written,
in the POSIX locale. In other locales, "standardinput" may
be replaced by something more appropriate in those locales.
−n Precede each output line by its relative line number in the
file, each file starting at line 1. The line number counter
shall be reset for each file processed.
−q Quiet. Nothing shall be written to the standard output,
regardless of matching lines. Exit with zero status if an
input line is selected.
−s Suppress the error messages ordinarily written for
nonexistent or unreadable files. Other error messages shall
not be suppressed.
−v Select lines not matching any of the specified patterns. If
the −v option is not specified, selected lines shall be
those that match any of the specified patterns.
−x Consider only input lines that use all characters in the
line excluding the terminating <newline> to match an entire
fixed string or regular expression to be matching lines.
The following operands shall be supported:
pattern_list
Specify one or more patterns to be used during the search
for input. This operand shall be treated as if it were
specified as −e pattern_list.
file A pathname of a file to be searched for the patterns. If no
file operands are specified, the standard input shall be
used.
The standard input shall be used if no file operands are specified,
and shall be used if a file operand is '−' and the implementation
treats the '−' as meaning standard input. Otherwise, the standard
input shall not be used. See the INPUT FILES section.
The input files shall be text files.
The following environment variables shall affect the execution of
grep:
LANG Provide a default value for the internationalization
variables that are unset or null. (See the Base Definitions
volume of POSIX.1‐2008, Section 8.2, Internationalization
Variables for the precedence of internationalization
variables used to determine the values of locale
categories.)
LC_ALL If set to a non-empty string value, override the values of
all the other internationalization variables.
LC_COLLATE
Determine the locale for the behavior of ranges,
equivalence classes, and multi-character collating elements
within regular expressions.
LC_CTYPE Determine the locale for the interpretation of sequences of
bytes of text data as characters (for example, single-byte
as opposed to multi-byte characters in arguments and input
files) and the behavior of character classes within regular
expressions.
LC_MESSAGES
Determine the locale that should be used to affect the
format and contents of diagnostic messages written to
standard error.
NLSPATH Determine the location of message catalogs for the
processing of LC_MESSAGES.
Default.
If the −l option is in effect, the following shall be written for
each file containing at least one selected input line:
"%s\n", <file>
Otherwise, if more than one file argument appears, and −q is not
specified, the grep utility shall prefix each output line by:
"%s:", <file>
The remainder of each output line shall depend on the other options
specified:
* If the −c option is in effect, the remainder of each output line
shall contain:
"%d\n", <count>
* Otherwise, if −c is not in effect and the −n option is in effect,
the following shall be written to standard output:
"%d:", <line number>
* Finally, the following shall be written to standard output:
"%s", <selected-line contents>
The standard error shall be used only for diagnostic messages.
None.
None.
The following exit values shall be returned:
0 One or more lines were selected.
1 No lines were selected.
>1 An error occurred.
If the −q option is specified, the exit status shall be zero if an
input line is selected, even if an error was detected. Otherwise,
default actions shall be performed.
The following sections are informative.
Care should be taken when using characters in pattern_list that may
also be meaningful to the command interpreter. It is safest to
enclose the entire pattern_list argument in single-quotes:
'...'
The −e pattern_list option has the same effect as the pattern_list
operand, but is useful when pattern_list begins with the <hyphen>
delimiter. It is also useful when it is more convenient to provide
multiple patterns as separate arguments.
Multiple −e and −f options are accepted and grep uses all of the
patterns it is given while matching input text lines. (Note that the
order of evaluation is not specified. If an implementation finds a
null string as a pattern, it is allowed to use that pattern first,
matching every line, and effectively ignore any other patterns.)
The −q option provides a means of easily determining whether or not a
pattern (or string) exists in a group of files. When searching
several files, it provides a performance improvement (because it can
quit as soon as it finds the first match) and requires less care by
the user in choosing the set of files to supply as arguments (because
it exits zero if it finds a match even if grep detected an access or
read error on earlier file operands).
1. To find all uses of the word "Posix" (in any case) in file
text.mm and write with line numbers:
grep −i −n posix text.mm
2. To find all empty lines in the standard input:
grep ^$
or:
grep −v .
3. Both of the following commands print all lines containing strings
"abc" or "def" or both:
grep −E 'abc|def'
grep −F 'abc
def'
4. Both of the following commands print all lines matching exactly
"abc" or "def":
grep −E '^abc$|^def$'
grep −F −x 'abc
def'
This grep has been enhanced in an upwards-compatible way to provide
the exact functionality of the historical egrep and fgrep commands as
well. It was the clear intention of the standard developers to
consolidate the three greps into a single command.
The old egrep and fgrep commands are likely to be supported for many
years to come as implementation extensions, allowing historical
applications to operate unmodified.
Historical implementations usually silently ignored all but one of
multiply-specified −e and −f options, but were not consistent as to
which specification was actually used.
The −b option was omitted from the OPTIONS section because block
numbers are implementation-defined.
The System V restriction on using − to mean standard input was
omitted.
A definition of action taken when given a null BRE or ERE is
specified. This is an error condition in some historical
implementations.
The −l option previously indicated that its use was undefined when no
files were explicitly named. This behavior was historical and placed
an unnecessary restriction on future implementations. It has been
removed.
The historical BSD grep −s option practice is easily duplicated by
redirecting standard output to /dev/null. The −s option required
here is from System V.
The −x option, historically available only with fgrep, is available
here for all of the non-obsolescent versions.
None.
sed(1p)
The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
Variables, Chapter 9, Regular Expressions, Section 12.2, Utility
Syntax Guidelines
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The Open
Group Base Specifications Issue 7, Copyright (C) 2013 by the
Institute of Electrical and Electronics Engineers, Inc and The Open
Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
applied.) In the event of any discrepancy between this version and
the original IEEE and The Open Group Standard, the original IEEE and
The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the
source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 GREP(1P)
Pages that refer to this page: awk(1p), cut(1p), paste(1p), sed(1p)