GNU Info
(grep.info)Invoking
Invoking `grep'
***************
`grep' comes with a rich set of options from POSIX.2 and GNU
extensions.
`-c'
`--count'
Suppress normal output; instead print a count of matching lines
for each input file. With the `-v', `--invert-match' option,
count non-matching lines.
`-e PATTERN'
`--regexp=PATTERN'
Use PATTERN as the pattern; useful to protect patterns beginning
with a `-'.
`-f FILE'
`--file=FILE'
Obtain patterns from FILE, one per line. The empty file contains
zero patterns, and therefore matches nothing.
`-i'
`--ignore-case'
Ignore case distinctions in both the pattern and the input files.
`-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
of every file will stop on the first match.
`-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 of every file will
stop on the first match. Also see the `-s' or `--no-messages'
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.
`-v'
`--invert-match'
Invert the sense of matching, to select non-matching lines.
`-x'
`--line-regexp'
Select only those matches that exactly match the whole line.
GNU Extensions
==============
`-A NUM'
`--after-context=NUM'
Print NUM lines of trailing context after matching lines.
`-B NUM'
`--before-context=NUM'
Print NUM lines of leading context before matching lines.
`-C NUM'
`--context=[NUM]'
Print NUM lines (default 2) of output context.
`-NUM'
Same as `--context=NUM' lines of leading and trailing context.
However, grep will never print any given line more than once.
`-V'
`--version'
Print the version number of `grep' to the standard output stream.
This version number should be included in all bug reports.
`--help'
Print a usage message briefly summarizing these command-line
options and the bug-reporting address, then exit.
`--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:_
`--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.
`-b'
`--byte-offset'
Print the byte offset within the input file before each line of
output. When `grep' runs on MS-DOS or MS-Windows, the printed
byte offsets depend on whether the `-u' (`--unix-byte-offsets')
option is used; see below.
`-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 (some operating systems and
filesystems disallow this, and will cause `grep' to print error
messages for every directory). 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.
`-H'
`--with-filename'
Print the filename for each match.
`-h'
`--no-filename'
Suppress the prefixing of filenames on output when multiple files
are searched.
`-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 of every file will stop on the first match.
`-a'
`--text'
Process a binary file as if it were text; this is equivalent to the
`--binary-files=text' option.
`-I'
Process a binary file as if it did not contain matching data; this
is equivalent to the `--binary-files=without-match' option.
`-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.
`-r'
`--recursive'
For each directory mentioned in the command line, read and process
all files in that directory, recursively. This is the same as the
`-d recurse' option.
`-y'
Obsolete synonym for `-i'.
`-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.
`-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., the byte offsets ignore the `CR' characters which were
stripped. 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.
`--mmap'
If possible, use the `mmap' system call to read input, instead of
the default `read' 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.
`-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.
`-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.
Several additional options control which variant of the `grep'
matching engine is used. Note: Grep Programs.
Environment Variables
=====================
Grep's behavior is affected by the following 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 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 variables 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 characters 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.
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