Generic Program Information¶

--help

Output a usage message and exit.

-V, --version

Output the version number of grep and exit.

Matcher Selection¶

-E, --extended-regexp

Interpret PATTERNS as extended regular expressions (EREs, see below).

-F, --fixed-strings

Interpret PATTERNS as fixed strings, not regular expressions.

-G, --basic-regexp

Interpret PATTERNS as basic regular expressions (BREs, see below). This is the default.

-P, --perl-regexp

Interpret PATTERNS as Perl-compatible regular expressions (PCREs). This option is experimental when combined with the -z (--null-data) option, and grep -P may warn of unimplemented features.

Matching Control¶

-e PATTERNS, --regexp=PATTERNS

Use PATTERNS as the patterns. If this option is used multiple times or is combined with the -f (--file) option, search for all patterns given. This option can be used to protect a pattern beginning with “-”.

-f FILE, --file=FILE

Obtain patterns from FILE, one per line. If this option is used multiple times or is combined with the -e (--regexp) option, search for all patterns given. The empty file contains zero patterns, and therefore matches nothing.

-i, --ignore-case

Ignore case distinctions, so that characters that differ only in case match each other.

-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 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. This option has no effect if -x is also specified.

-x, --line-regexp

Select only those matches that exactly match the whole line. For a regular expression pattern, this is like parenthesizing the pattern and then surrounding it with ^ and $.

-y

Obsolete synonym for -i.

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.

--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.

-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.

-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.

-o, --only-matching

Print only the matched (non-empty) parts of a matching line, with each such part on a separate output line.

-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.

-s, --no-messages

Suppress error messages about nonexistent or unreadable files.

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.

-H, --with-filename

Print the file name for each match. This is the default when there is more than one file to search.

-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.

--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.

-n, --line-number

Prefix each line of output with the 1-based line number within its input file.

-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.

-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.

-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.

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.

-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.

-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.

File and Directory Selection¶

-a, --text

Process a binary file as if it were text; this is equivalent to the --binary-files=text option.

--binary-files=TYPE

If a file's data or metadata indicate that the file contains binary data, assume that the file is of type TYPE. Non-text bytes indicate binary data; these are either output bytes that are improperly encoded for the current locale, or null input bytes when the -z option is not given.

By default, TYPE is binary, and when grep discovers that a file is binary it suppresses any further output, and instead 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, when grep discovers that a file is binary it assumes that the rest of the 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.

When type is binary, grep may treat non-text bytes as line terminators even without the -z option. This means choosing binary versus text can affect whether a pattern matches a file. For example, when type is binary the pattern q$ might match q immediately followed by a null byte, even though this is not matched when type is text. Conversely, when type is binary the pattern . (period) might not match a null byte.

Warning: The -a option 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. On the other hand, when reading files whose text encodings are unknown, it can be helpful to use -a or to set LC_ALL='C' in the environment, in order to find more matches even if the matches are unsafe for direct display.

-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.

-d ACTION, --directories=ACTION

If an input file is a directory, use ACTION to process it. By default, ACTION is read, i.e., read directories just as if they were ordinary files. If ACTION is skip, silently skip directories. If ACTION is recurse, read all files under each directory, recursively, following symbolic links only if they are on the command line. This is equivalent to the -r option.

--exclude=GLOB

Skip any command-line file with a name suffix that matches the pattern GLOB, using wildcard matching; a name suffix is either the whole name, or any suffix starting after a / and before a non-/. When searching recursively, skip any subfile whose base name matches GLOB; the base name is the part after the last /. A pattern can use *, ?, and [...] as wildcards, and \ to quote a wildcard or backslash character literally.

--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).

--exclude-dir=GLOB

Skip any command-line directory with a name suffix that matches the pattern GLOB. When searching recursively, skip any subdirectory whose base name matches GLOB. Ignore any redundant trailing slashes in GLOB.

-I

Process a binary file as if it did not contain matching data; this is equivalent to the --binary-files=without-match option.

--include=GLOB

Search only files whose base name matches GLOB (using wildcard matching as described under --exclude).

-r, --recursive

Read all files under each directory, recursively, following symbolic links only if they are on the command line. Note that if no file operand is given, grep searches the working directory. This is equivalent to the -d recurse option.

-R, --dereference-recursive

Read all files under each directory, recursively. Follow all symbolic links, unlike -r.

Other Options¶

--line-buffered

Use line buffering on output. This can cause a performance penalty.

-U, --binary

Treat the file(s) as binary. By default, under MS-DOS and MS-Windows, grep guesses whether a file is text or binary as described for the --binary-files option. 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.

-z, --null-data

Treat input and output data as sequences 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.

Character Classes and Bracket Expressions¶

Within a bracket expression, a range expression consists of two characters separated by a hyphen. It matches any single character that sorts between the two characters, inclusive, using the locale's collating sequence and character set. For example, in the default C locale, [a-d] is equivalent to [abcd]. Many locales sort characters in dictionary order, and in these locales [a-d] is typically not equivalent to [abcd]; it might be equivalent to [aBbCcDd], for example. To obtain the traditional interpretation of bracket expressions, you can use the C locale by setting the LC_ALL environment variable to the value C.

Finally, certain named classes of characters are predefined within bracket expressions, as follows. Their names are self explanatory, and they are [:alnum:], [:alpha:], [:cntrl:], [:digit:], [:graph:], [:lower:], [:print:], [:punct:], [:space:], [:upper:], and [:xdigit:]. For example, [[:alnum:]] means the character class of numbers and letters in the current locale. In the C locale and ASCII character set encoding, this is the same as [0-9A-Za-z]. (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 expression.) Most meta-characters lose their special meaning inside bracket expressions. To include a literal ] place it first in the list. Similarly, to include a literal ^ place it anywhere but first. Finally, to include a literal - place it last.

Anchoring¶

The Backslash Character and Special Expressions¶

Repetition¶

?

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.

{,m}

The preceding item is matched at most m times. This is a GNU extension.

{n,m}

The preceding item is matched at least n times, but not more than m times.

Concatenation¶

Alternation¶

Precedence¶

Back References and Subexpressions¶

Basic vs Extended Regular Expressions¶

Reporting Bugs¶

Known Bugs¶

Back-references are very slow, and may require exponential time.

Regular Manual Pages¶

POSIX Programmer's Manual Page¶

Full Documentation¶

info grep

should give you access to the complete manual.