SunOS man pages : grep (1)
User Commands GREP(1)
NAME
grep, egrep, fgrep - print lines matching a pattern
SYNOPSIS
grep [options] PATTERN [FILE...]
grep [options] [-e PATTERN | -f FILE] [FILE...]
DESCRIPTION
Grep searches the named input FILEs (or standard input if no
files are named, or the file name - is given) for lines con-
taining a match to the given PATTERN. By default, grep
prints the matching lines.
In addition, two variant programs egrep and fgrep are avail-
able. Egrep is the same as grep -E. Fgrep is the same as
grep -F.
OPTIONS
-A NUM, --after-context=NUM
Print NUM lines of trailing context after matching
lines.
-a, --text
Process a binary file as if it were text; this is
equivalent to the --binary-files=text option.
-B NUM, --before-context=NUM
Print NUM lines of leading context before matching
lines.
-C [NUM], -NUM, --context[=NUM]
Print NUM lines (default 2) of output context.
-b, --byte-offset
Print the byte offset within the input file before each
line of output.
--binary-files=TYPE
If the first few bytes of a file indicate that the file
contains binary data, assume that the file is of type
TYPE. By default, TYPE is binary, and grep normally
outputs either a one-line message saying that a binary
file matches, or no message if there is no match. If
TYPE is without-match, grep assumes that a binary file
does not match; this is equivalent to the -I option.
If TYPE is text, grep processes a binary file as if it
were text; this is equivalent to the -a option. Warn-
ing: grep --binary-files=text might output binary gar-
bage, which can have nasty side effects if the output
is a terminal and if the terminal driver interprets
some of it as commands.
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-c, --count
Suppress normal output; instead print a count of match-
ing lines for each input file. With the -v, --invert-
match option (see below), count non-matching lines.
-d ACTION, --directories=ACTION
If an input file is a directory, use ACTION to process
it. By default, ACTION is read, which means that
directories are read just as if they were ordinary
files. If ACTION is skip, directories are silently
skipped. If ACTION is recurse, grep reads all files
under each directory, recursively; this is equivalent
to the -r option.
-E, --extended-regexp
Interpret PATTERN as an extended regular expression
(see below).
-e PATTERN, --regexp=PATTERN
Use PATTERN as the pattern; useful to protect patterns
beginning with -.
-F, --fixed-strings
Interpret PATTERN as a list of fixed strings, separated
by newlines, any of which is to be matched.
-f FILE, --file=FILE
Obtain patterns from FILE, one per line. The empty
file contains zero patterns, and therefore matches
nothing.
-G, --basic-regexp
Interpret PATTERN as a basic regular expression (see
below). This is the default.
-H, --with-filename
Print the filename for each match.
-h, --no-filename
Suppress the prefixing of filenames on output when mul-
tiple files are searched.
--help
Output a brief help message.
-I Process a binary file as if it did not contain matching
data; this is equivalent to the --binary-
files=without-match option.
-i, --ignore-case
Ignore case distinctions in both the PATTERN and the
input files.
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-L, --files-without-match
Suppress normal output; instead print the name of each
input file from which no output would normally have
been printed. The scanning will stop on the first
match.
-l, --files-with-matches
Suppress normal output; instead print the name of each
input file from which output would normally have been
printed. The scanning will stop on the first match.
--mmap
If possible, use the mmap(2) system call to read input,
instead of the default read(2) system call. In some
situations, --mmap yields better performance. However,
--mmap can cause undefined behavior (including core
dumps) if an input file shrinks while grep is operat-
ing, or if an I/O error occurs.
-n, --line-number
Prefix each line of output with the line number within
its input file.
-q, --quiet, --silent
Quiet; suppress normal output. The scanning will stop
on the first match. Also see the -s or --no-messages
option below.
-r, --recursive
Read all files under each directory, recursively; this
is equivalent to the -d recurse option.
-s, --no-messages
Suppress error messages about nonexistent or unreadable
files. Portability note: unlike GNU grep, traditional
grep did not conform to POSIX.2, because traditional
grep lacked a -q option and its -s option behaved like
GNU grep's -q option. Shell scripts intended to be
portable to traditional grep should avoid both -q and
-s and should redirect output to /dev/null instead.
-U, --binary
Treat the file(s) as binary. By default, under MS-DOS
and MS-Windows, grep guesses the file type by looking
at the contents of the first 32KB read from the file.
If grep decides the file is a text file, it strips the
CR characters from the original file contents (to make
regular expressions with ^ and $ work correctly).
Specifying -U overrules this guesswork, causing all
files to be read and passed to the matching mechanism
verbatim; if the file is a text file with CR/LF pairs
at the end of each line, this will cause some regular
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expressions to fail. This option has no effect on
platforms other than MS-DOS and MS-Windows.
-u, --unix-byte-offsets
Report Unix-style byte offsets. This switch causes
grep to report byte offsets as if the file were Unix-
style text file, i.e. with CR characters stripped off.
This will produce results identical to running grep on
a Unix machine. This option has no effect unless -b
option is also used; it has no effect on platforms
other than MS-DOS and MS-Windows.
-V, --version
Print the version number of grep to standard error.
This version number should be included in all bug
reports (see below).
-v, --invert-match
Invert the sense of matching, to select non-matching
lines.
-w, --word-regexp
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.
-x, --line-regexp
Select only those matches that exactly match the whole
line.
-y Obsolete synonym for -i.
-Z, --null
Output a zero byte (the ASCII NUL character) instead of
the character that normally follows a file name. For
example, grep -lZ outputs a zero byte after each file
name instead of the usual newline. This option makes
the output unambiguous, even in the presence of file
names containing unusual characters like newlines.
This option can be used with commands like find
-print0, perl -0, sort -z, and xargs -0 to process
arbitrary file names, even those that contain newline
characters.
REGULAR EXPRESSIONS
A regular expression is a pattern that describes a set of
strings. Regular expressions are constructed analogously to
arithmetic expressions, by using various operators to
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combine smaller expressions.
Grep understands two different versions of regular expres-
sion syntax: "basic" and "extended." In GNU grep, there is
no difference in available functionality using either syn-
tax. In other implementations, basic regular expressions
are less powerful. The following description applies to
extended regular expressions; differences for basic regular
expressions are summarized afterwards.
The fundamental building blocks are the regular expressions
that match a single character. Most characters, including
all letters and digits, are regular expressions that match
themselves. Any metacharacter with special meaning may be
quoted by preceding it with a backslash.
A list of characters enclosed by [ and ] matches any single
character in that list; if the first character of the list
is the caret ^ then it matches any character not in the
list. For example, the regular expression [0123456789]
matches any single digit. A range of characters may be
specified by giving the first and last characters, separated
by a hyphen. Finally, certain named classes of characters
are predefined. Their names are self explanatory, and they
are [:alnum:], [:alpha:], [:cntrl:], [:digit:], [:graph:],
[:lower:], [:print:], [:punct:], [:space:], [:upper:], and
[:xdigit:]. For example, [[:alnum:]] means [0-9A-Za-z],
except the latter form depends upon the POSIX locale and the
ASCII character encoding, whereas the former is independent
of locale and character set. (Note that the brackets in
these class names are part of the symbolic names, and must
be included in addition to the brackets delimiting the
bracket list.) Most metacharacters lose their special mean-
ing inside lists. To include a literal ] place it first in
the list. Similarly, to include a literal ^ place it any-
where but first. Finally, to include a literal - place it
last.
The period . matches any single character. The symbol \w is
a synonym for [[:alnum:]] and \W is a synonym for
[^[:alnum]].
The caret ^ and the dollar sign $ are metacharacters that
respectively match the empty string at the beginning and end
of a line. The symbols \< and \> respectively match the
empty string at the beginning and end of a word. The symbol
\b matches the empty string at the edge of a word, and \B
matches the empty string provided it's not at the edge of a
word.
A regular expression may be followed by one of several
repetition operators:
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? The preceding item is optional and matched at most
once.
* The preceding item will be matched zero or more times.
+ The preceding item will be matched one or more times.
{n} The preceding item is matched exactly n times.
{n,} The preceding item is matched n or more times.
{n,m}
The preceding item is matched at least n times, but not
more than m times.
Two regular expressions may be concatenated; the resulting
regular expression matches any string formed by concatenat-
ing two substrings that respectively match the concatenated
subexpressions.
Two regular expressions may be joined by the infix operator
|; the resulting regular expression matches any string
matching either subexpression.
Repetition takes precedence over concatenation, which in
turn takes precedence over alternation. A whole subexpres-
sion may be enclosed in parentheses to override these pre-
cedence rules.
The backreference \n, where n is a single digit, matches the
substring previously matched by the nth parenthesized subex-
pression of the regular expression.
In basic regular expressions the metacharacters ?, +, {, |,
(, and ) lose their special meaning; instead use the
backslashed versions \?, \+, \{, \|, \(, and \).
Traditional egrep did not support the { metacharacter, and
some egrep implementations support \{ instead, so portable
scripts should avoid { in egrep patterns and should use [{]
to match a literal {.
GNU egrep attempts to support traditional usage by assuming
that { is not special if it would be the start of an invalid
interval specification. For example, the shell command
egrep '{1' searches for the two-character string {1 instead
of reporting a syntax error in the regular expression.
POSIX.2 allows this behavior as an extension, but portable
scripts should avoid it.
ENVIRONMENT VARIABLES
GREP_OPTIONS
This variable specifies default options to be placed in
front of any explicit options. For example, if
GREP_OPTIONS is '--binary-files=without-match
--directories=skip', grep behaves as if the two options
--binary-files=without-match and --directories=skip had
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been specified before any explicit options. Option
specifications are separated by whitespace. A
backslash escapes the next character, so it can be used
to specify an option containing whitespace or a
backslash.
LC_ALL, LC_MESSAGES, LANG
These variables specify the LC_MESSAGES locale, which
determines the language that grep uses for messages.
The locale is determined by the first of these vari-
ables that is set. American English is used if none of
these environment variables are set, or if the message
catalog is not installed, or if grep was not compiled
with national language support (NLS).
LC_ALL, LC_CTYPE, LANG
These variables specify the LC_CTYPE locale, which
determines the type of characters, e.g., which charac-
ters are whitespace. The locale is determined by the
first of these variables that is set. The POSIX locale
is used if none of these environment variables are set,
or if the locale catalog is not installed, or if grep
was not compiled with national language support (NLS).
POSIXLY_CORRECT
If set, grep behaves as POSIX.2 requires; otherwise,
grep behaves more like other GNU programs. POSIX.2
requires that options that follow file names must be
treated as file names; by default, such options are
permuted to the front of the operand list and are
treated as options. Also, POSIX.2 requires that
unrecognized options be diagnosed as "illegal", but
since they are not really against the law the default
is to diagnose them as "invalid". POSIXLY_CORRECT also
disables _N_GNU_nonoption_argv_flags_, described below.
_N_GNU_nonoption_argv_flags_
(Here N is grep's numeric process ID.) If the ith
character of this environment variable's value is 1, do
not consider the ith operand of grep to be an option,
even if it appears to be one. A shell can put this
variable in the environment for each command it runs,
specifying which operands are the results of file name
wildcard expansion and therefore should not be treated
as options. This behavior is available only with the
GNU C library, and only when POSIXLY_CORRECT is not
set.
DIAGNOSTICS
Normally, exit status is 0 if matches were found, and 1 if
no matches were found. (The -v option inverts the sense of
the exit status.) Exit status is 2 if there were syntax
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errors in the pattern, inaccessible input files, or other
system errors.
BUGS
Email bug reports to bug-gnu-utils@gnu.org. Be sure to
include the word "grep" somewhere in the "Subject:" field.
Large repetition counts in the {m,n} construct may cause
grep to use lots of memory. In addition, certain other
obscure regular expressions require exponential time and
space, and may cause grep to run out of memory.
Backreferences are very slow, and may require exponential
time.
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