Originální popis anglicky:
grep - search a file for a pattern
Návod, kniha: POSIX Programmer's Manual
grep [-E| -F][-c| -l|
-q][-insvx ] -e pattern_list...
[-f
pattern_file]...[file...]
grep
[-E| -F][-c| -l|
-q
][-insvx][-e
pattern_list]...
-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>s; the
pattern_file's contents shall consist of one or more patterns
terminated by <newline>. 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 IEEE Std 1003.1-2001, 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>s) 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
IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001, 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>s 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
IEEE Std 1003.1-2001, 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 IEEE Std 1003.1-2001, Section
9.3, Basic Regular Expressions.
- -i
- Perform pattern matching in searches without regard to
case; see the Base Definitions volume of
IEEE Std 1003.1-2001, 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
"(standard input)" shall be written, in the POSIX locale.
In other locales, "standard input" 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 only if no
file operands are specified.
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
IEEE Std 1003.1-2001, 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, and the
-q option is not, the
following shall be written for each file containing at least one selected
input line:
Otherwise, if more than one
file argument appears, and
-q is not
specified, the
grep utility shall prefix each output line by:
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:
- *
- Otherwise, if -c is not in effect and the -n
option is in effect, the following shall be written to standard output:
- *
- 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:
- 2.
- To find all empty lines in the standard input:
or:
- 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
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html
.
