grep searches the named input FILEs (or standard input if no files are named, or if a single hyphen-minus
(-) is given as file name) for lines containing a match to the given PATTERN. By default, grep prints
the matching lines.
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Generic Program Information
--help Print a usage message briefly summarizing these command-line options and the bug-reporting
address, then exit.
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-V, --version
Print the version number of grep to the standard output stream. This version number should be
included in all bug reports (see below).
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Matcher Selection
-E, --extended-regexp
Interpret PATTERN as an extended regular expression (ERE, see below). (-E is specified by POSIX.)
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-F, --fixed-strings
Interpret PATTERN as a list of fixed strings, separated by newlines, any of which is to be
matched. (-F is specified by POSIX.)
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-G, --basic-regexp
Interpret PATTERN as a basic regular expression (BRE, see below). This is the default.
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-P, --perl-regexp
Interpret PATTERN as a Perl regular expression (PCRE, see below). This is highly experimental and
grep -P may warn of unimplemented features.
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Matching Control
-e PATTERN, --regexp=PATTERN
Use PATTERN as the pattern. This can be used to specify multiple search patterns, or to protect a
pattern beginning with a hyphen (-). (-e is specified by POSIX.)
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-f FILE, --file=FILE
Obtain patterns from FILE, one per line. The empty file contains zero patterns, and therefore
matches nothing. (-f is specified by POSIX.)
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-i, --ignore-case
Ignore case distinctions in both the PATTERN and the input files. (-i is specified by POSIX.)
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-v, --invert-match
Invert the sense of matching, to select non-matching lines. (-v is specified by POSIX.)
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-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 preceded 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.
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-x, --line-regexp
Select only those matches that exactly match the whole line. (-x is specified by POSIX.)
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-y Obsolete synonym for -i.
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General Output Control
-c, --count
Suppress normal output; instead print a count of matching lines for each input file. With the -v,
--invert-match option (see below), count non-matching lines. (-c is specified by POSIX.)
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--color[=WHEN], --colour[=WHEN]
Surround the matched (non-empty) strings, matching lines, context lines, file names, line numbers,
byte offsets, and separators (for fields and groups of context lines) with escape sequences to
display them in color on the terminal. The colors are defined by the environment variable
GREP_COLORS. The deprecated environment variable GREP_COLOR is still supported, but its setting
does not have priority. WHEN is never, always, or auto.
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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.
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-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. (-l is specified by POSIX.)
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-m NUM, --max-count=NUM
Stop reading a file after NUM matching lines. If the input is standard input from a regular file,
and NUM matching lines are output, grep ensures that the standard input is positioned to just
after the last matching line before exiting, regardless of the presence of trailing context lines.
This enables a calling process to resume a search. When grep stops after NUM matching lines, it
outputs any trailing context lines. When the -c or --count option is also used, grep does not
output a count greater than NUM. When the -v or --invert-match option is also used, grep stops
after outputting NUM non-matching lines.
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-o, --only-matching
Print only the matched (non-empty) parts of a matching line, with each such part on a separate
output line.
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-q, --quiet, --silent
Quiet; do not write anything to standard output. Exit immediately with zero status if any match
is found, even if an error was detected. Also see the -s or --no-messages option. (-q is
specified by POSIX.)
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-s, --no-messages
Suppress error messages about nonexistent or unreadable files. Portability note: unlike GNU grep,
7th Edition Unix grep did not conform to POSIX, because it lacked -q and its -s option behaved
like GNU grep's -q option. USG-style grep also lacked -q but its -s option behaved like GNU grep.
Portable shell scripts should avoid both -q and -s and should redirect standard and error output
to /dev/null instead. (-s is specified by POSIX.)
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Output Line Prefix Control
-b, --byte-offset
Print the 0-based byte offset within the input file before each line of output. If -o
(--only-matching) is specified, print the offset of the matching part itself.
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-H, --with-filename
Print the file name for each match. This is the default when there is more than one file to
search.
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-h, --no-filename
Suppress the prefixing of file names on output. This is the default when there is only one file
(or only standard input) to search.
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--label=LABEL
Display input actually coming from standard input as input coming from file LABEL. This is
especially useful when implementing tools like zgrep, e.g., gzip -cd foo.gz | grep --label=foo -H
something. See also the -H option.
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-n, --line-number
Prefix each line of output with the 1-based line number within its input file. (-n is specified
by POSIX.)
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-T, --initial-tab
Make sure that the first character of actual line content lies on a tab stop, so that the
alignment of tabs looks normal. This is useful with options that prefix their output to the
actual content: -H,-n, and -b. In order to improve the probability that lines from a single file
will all start at the same column, this also causes the line number and byte offset (if present)
to be printed in a minimum size field width.
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-u, --unix-byte-offsets
Report Unix-style byte offsets. This switch causes grep to report byte offsets as if the file
were a 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.
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-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.
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Context Line Control
-A NUM, --after-context=NUM
Print NUM lines of trailing context after matching lines. Places a line containing a group
separator (--) between contiguous groups of matches. With the -o or --only-matching option, this
has no effect and a warning is given.
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-B NUM, --before-context=NUM
Print NUM lines of leading context before matching lines. Places a line containing a group
separator (--) between contiguous groups of matches. With the -o or --only-matching option, this
has no effect and a warning is given.
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-C NUM, -NUM, --context=NUM
Print NUM lines of output context. Places a line containing a group separator (--) between
contiguous groups of matches. With the -o or --only-matching option, this has no effect and a
warning is given.
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File and Directory Selection
-a, --text
Process a binary file as if it were text; this is equivalent to the --binary-files=text option.
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--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.
Warning: grep --binary-files=text might output binary garbage, 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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-D ACTION, --devices=ACTION
If an input file is a device, FIFO or socket, use ACTION to process it. By default, ACTION is
read, which means that devices are read just as if they were ordinary files. If ACTION is skip,
devices are silently skipped.
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-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.
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--exclude=GLOB
Skip files whose base name matches GLOB (using wildcard matching). A file-name glob can use *, ?,
and [...] as wildcards, and \ to quote a wildcard or backslash character literally.
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--exclude-from=FILE
Skip files whose base name matches any of the file-name globs read from FILE (using wildcard
matching as described under --exclude).
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--exclude-dir=DIR
Exclude directories matching the pattern DIR from recursive searches.
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-I Process a binary file as if it did not contain matching data; this is equivalent to the
--binary-files=without-match option.
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--include=GLOB
Search only files whose base name matches GLOB (using wildcard matching as described under
--exclude).
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-R, -r, --recursive
Read all files under each directory, recursively; this is equivalent to the -d recurse option.
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Other Options
--line-buffered
Use line buffering on output. This can cause a performance penalty.
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--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 operating, or if an I/O
error occurs.
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-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 expressions to fail. This
option has no effect on platforms other than MS-DOS and MS-Windows.
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-z, --null-data
Treat the input as a set of lines, each terminated by a zero byte (the ASCII NUL character)
instead of a newline. Like the -Z or --null option, this option can be used with commands like
sort -z to process arbitrary file names.
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