Name
grep - search a file for a pattern
Synopsis
/usr/bin/grep [-c | -l | -q] [-bhinsvw] limited-regular-expression
[filename]...
/usr/xpg4/bin/grep [-E | -F] [-c | -l | -q] [-bhinsvx] -e pattern_list...
[-f pattern_file]... [file]...
/usr/xpg4/bin/grep [-E | -F] [-c | -l | -q] [-bhinsvx]
[-e pattern_list]... -f pattern_file... [file]...
/usr/xpg4/bin/grep [-E | -F] [-c | -l | -q] [-bhinsvx] pattern
[file]...
Description
The grep utility searches text files for a pattern and
prints all lines that contain that pattern. It uses a com-
pact non-deterministic algorithm.
Be careful using the characters $, *, [, ^, |, (, ), and \
in the pattern_list because they are also meaningful to the
shell. It is safest to enclose the entire pattern_list in
single quotes a'...a'.
If no files are specified, grep assumes standard input. Nor-
mally, each line found is copied to standard output. The
file name is printed before each line found if there is more
than one input file.
/usr/bin/grep
The /usr/bin/grep utility uses limited regular expressions
like those described on the regexp(5) manual page to match
the patterns.
/usr/xpg4/bin/grep
The options -E and -F affect the way /usr/xpg4/bin/grep
interprets pattern_list. If -E is specified,
/usr/xpg4/bin/grep interprets pattern_list as a full regular
expression (see -E for description). If -F is specified,
grep interprets pattern_list as a fixed string. If neither
are specified, grep interprets pattern_list as a basic regu-
lar expression as described on regex(5) manual page.
Options
The following options are supported for both /usr/bin/grep
and /usr/xpg4/bin/grep:
-b
Precedes each line by the block number on which it was
found. This can be useful in locating block numbers by
context (first block is 0).
-c
Prints only a count of the lines that contain the pat-
tern.
-h
Prevents the name of the file containing the matching
line from being prepended to that line. Used when
searching multiple files.
-i
Ignores upper/lower case distinction during comparis-
ons.
-l
Prints only the names of files with matching lines,
separated by NEWLINE characters. Does not repeat the
names of files when the pattern is found more than
once.
-n
Precedes each line by its line number in the file
(first line is 1).
-q
Quiet. Does not write anything to the standard output,
regardless of matching lines. Exits with zero status
if an input line is selected.
-s
Suppresses error messages about nonexistent or unread-
able files.
-v
Prints all lines except those that contain the pat-
tern.
-w
Searches for the expression as a word as if surrounded
by \< and \>.
/usr/xpg4/bin/grep
The following options are supported for /usr/xpg4/bin/grep
only:
-e pattern_list
Specifies one or more patterns to be used
during the search for input. Patterns in
pattern_list must be separated by a NEW-
LINE character. A null pattern can be
specified by two adjacent newline charac-
ters in pattern_list. Unless the -E or -F
option is also specified, each pattern is
treated as a basic regular expression.
Multiple -e and -f options are accepted
by grep. All of the specified patterns
are used when matching lines, but the
order of evaluation is unspecified.
-E
Matches using full regular expressions.
Treats each pattern specified as a full
regular expression. If any entire full
regular expression pattern matches an
input line, the line is matched. A null
full regular expression matches every
line. Each pattern is interpreted as a
full regular expression as described on
the regex(5) manual page, except for \(
and \), and including:
1. A full regular expression fol-
lowed by + that matches one or
more occurrences of the full
regular expression.
2. A full regular expression fol-
lowed by ? that matches 0 or 1
occurrences of the full regular
expression.
3. Full regular expressions
separated by | or by a new-line
that match strings that are
matched by any of the expres-
sions.
4. A full regular expression that
is enclosed in parentheses ()
for grouping.
The order of precedence of operators is
[], then *?+, then concatenation, then |
and new-line.
-f pattern_file
Reads one or more patterns from the file
named by the path name pattern_file. Pat-
terns in pattern_file are terminated by a
NEWLINE character. A null pattern can be
specified by an empty line in
pattern_file. Unless the -E or -F option
is also specified, each pattern is
treated as a basic regular expression.
-F
Matches using fixed strings. Treats each
pattern specified as a string instead of
a regular expression. If an input line
contains any of the patterns as a con-
tiguous sequence of bytes, the line is
matched. A null string matches every
line. See fgrep(1) for more information.
-x
Considers only input lines that use all
characters in the line to match an entire
fixed string or regular expression to be
matching lines.
Operands
The following operands are supported:
file
A path name of a file to be searched for the pat-
terns. If no file operands are specified, the stan-
dard input is used.
/usr/bin/grep
pattern
Specifies a pattern to be used during the search
for input.
/usr/xpg4/bin/grep
pattern
Specifies one or more patterns to be used during
the search for input. This operand is treated as
if it were specified as -e pattern_list.
Usage
The -c, -l and -q options are mutually exclusive. If speci-
fied together -q overrides -c which overrides -l.
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 argu-
ments.
Multiple -e and -f options are accepted and grep uses all of
the patterns it is given while matching input text lines.
Notice 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).
Large File Behavior
See largefile(5) for the description of the behavior of grep
when encountering files greater than or equal to 2 Gbyte (
2^31 bytes).
Examples
Example 1 Finding All Uses of a Word
To find all uses of the word "Posix" (in any case) in the
file text.mm, and write with line numbers:
example% /usr/bin/grep -i -n posix text.mm
Example 2 Finding All Empty Lines
To find all empty lines in the standard input:
example% /usr/bin/grep ^$
or
example% /usr/bin/grep -v .
Example 3 Finding Lines Containing Strings
All of the following commands print all lines containing
strings abc or def or both:
example% /usr/xpg4/bin/grep `abc
def'
example% /usr/xpg4/bin/grep -e `abc
def'
example% /usr/xpg4/bin/grep -e `abc' -e `def'
example% /usr/xpg4/bin/grep -E `abc|def'
example% /usr/xpg4/bin/grep -E -e `abc|def'
example% /usr/xpg4/bin/grep -E -e `abc' -e `def'
example% /usr/xpg4/bin/grep -E `abc
def'
example% /usr/xpg4/bin/grep -E -e `abc
def'
example% /usr/xpg4/bin/grep -F -e `abc' -e `def'
example% /usr/xpg4/bin/grep -F `abc
def'
example% /usr/xpg4/bin/grep -F -e `abc
def'
Example 4 Finding Lines with Matching Strings
Both of the following commands print all lines matching
exactly abc or def:
example% /usr/xpg4/bin/grep -E `^abc$ ^def$'
example% /usr/xpg4/bin/grep -F -x `abc def'
Environment Variables
See environ(5) for descriptions of the following environment
variables that affect the execution of grep: LANG, LC_ALL,
LC_COLLATE, LC_CTYPE, LC_MESSAGES, and NLSPATH.
Exit Status
The following exit values are returned:
0
One or more matches were found.
1
No matches were found.
2
Syntax errors or inaccessible files (even if matches
were found).
Attributes
See attributes(5) for descriptions of the following attri-
butes:
/usr/bin/grep
tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRI-
BUTE TYPEATTRIBUTE VALUE _ Availabilitysystem/core-os _
CSINot Enabled
/usr/xpg4/bin/grep
tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i) ATTRI-
BUTE TYPEATTRIBUTE VALUE _ Availabilitysystem/xopen/xcu4 _
CSIEnabled _ Interface StabilityCommitted _ StandardSee
standards(5).
See Also
egrep(1), fgrep(1), sed(1), sh(1), attributes(5),
environ(5), largefile(5), regex(5), regexp(5), standards(5)
Notes
/usr/bin/grep
Lines are limited only by the size of the available virtual
memory. If there is a line with embedded nulls, grep only
matches up to the first null. If the line matches, the
entire line is printed.
/usr/xpg4/bin/grep
The results are unspecified if input files contain lines
longer than LINE_MAX bytes or contain binary data. LINE_MAX
is defined in /usr/include/limits.h.