Linux文本处理四剑客grep指令-man帮助手册

GREP(1) User Commands GREP(1)

NAME
grep, egrep, fgrep - print lines that match patterns

SYNOPSIS
grep [OPTION...] PATTERNS [FILE...]
grep [OPTION...] -e PATTERNS ... [FILE...]
grep [OPTION...] -f PATTERN_FILE ... [FILE...]

DESCRIPTION
grep searches for PATTERNS in each FILE. PATTERNS is one or more patterns separated
by newline characters, and grep prints each line that matches a pattern. Typically
PATTERNS should be quoted when grep is used in a shell command.

A FILE of “-” stands for standard input. If no FILE is given, recursive searches
examine the working directory, and nonrecursive searches read standard input.

In addition, the variant programs egrep and fgrep are the same as grep -E and
grep -F, respectively. These variants are deprecated, but are provided for backward
compatibility.

OPTIONS
Generic Program Information
--help Output a usage message and exit.

-V, --version
Output the version number of grep and exit.

Pattern Syntax
-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 in patterns and input data, so that characters that
differ only in case match each other.

--no-ignore-case
Do not ignore case distinctions in patterns and input data. This is the
default. This option is useful for passing to shell scripts that already use
-i, to cancel its effects because the two options override 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 can be useful for commands that transform a file's contents
before searching, e.g., gzip -cd foo.gz | grep --label=foo -H 'some pattern'.
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 (described under --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 (described under --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
(described under --group-separator) between contiguous groups of matches.
With the -o or --only-matching option, this has no effect and a warning is
given.

--group-separator=SEP
Use SEP as a group separator. By default SEP is double hyphen (--).

--no-group-separator
Use empty string as a group separator.

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 grep suppresses output after null input binary
data is discovered, and suppresses output lines that contain improperly
encoded data. When some output is suppressed, grep follows any output with a
one-line message saying that a binary file matches.

If TYPE is without-match, when grep discovers null input binary data 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 a trailing
part that starts with a non-slash character immediately after a slash (/) in
the name. When searching recursively, skip any subfile whose base name
matches GLOB; the base name is the part after the last slash. 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). If contradictory --include and --exclude options
are given, the last matching one wins. If no --include or --exclude options
match, a file is included unless the first such option is --include.

-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.

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 combine smaller expressions.

grep understands three different versions of regular expression syntax: “basic”
(BRE), “extended” (ERE) and “perl” (PCRE). In GNU grep there is no difference in
available functionality between basic and extended syntaxes. 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. Perl-compatible regular expressions give
additional functionality, and are documented in pcresyntax(3) and pcrepattern(3), but
work only if PCRE is available in the system.

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 meta-character with special meaning may be
quoted by preceding it with a backslash.

The period . matches any single character. It is unspecified whether it matches an
encoding error.

Character Classes and Bracket Expressions
A bracket expression is a list of characters enclosed by [ and ]. It 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; it is unspecified whether it matches
an encoding error. For example, the regular expression [0123456789] matches any
single digit.

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:], [:blank:], [: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 caret ^ and the dollar sign $ are meta-characters that respectively match the
empty string at the beginning and end of a line.

The Backslash Character and Special Expressions
The symbols < and > respectively match the empty string at the beginning and end of
a word. The symbol 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. The symbol w is a synonym
for [_[:alnum:]] and W is a synonym for [^_[:alnum:]].

Repetition
A regular expression may be followed by one of several repetition operators:
? 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
Two regular expressions may be concatenated; the resulting regular expression matches
any string formed by concatenating two substrings that respectively match the
concatenated expressions.

Alternation
Two regular expressions may be joined by the infix operator |; the resulting regular
expression matches any string matching either alternate expression.

Precedence
Repetition takes precedence over concatenation, which in turn takes precedence over
alternation. A whole expression may be enclosed in parentheses to override these
precedence rules and form a subexpression.

Back-references and Subexpressions
The back-reference
, where n is a single digit, matches the substring previously
matched by the nth parenthesized subexpression of the regular expression.

Basic vs Extended Regular Expressions
In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their
special meaning; instead use the backslashed versions ?, +, {, |, (, and ).

EXIT STATUS
Normally the exit status is 0 if a line is selected, 1 if no lines were selected, and
2 if an error occurred. However, if the -q or --quiet or --silent is used and a line
is selected, the exit status is 0 even if an error occurred.

ENVIRONMENT
The behavior of grep is affected by the following environment variables.

The locale for category LC_foo is specified by examining the three environment
variables LC_ALL, LC_foo, LANG, in that order. The first of these variables that is
set specifies the locale. For example, if LC_ALL is not set, but LC_MESSAGES is set
to pt_BR, then the Brazilian Portuguese locale is used for the LC_MESSAGES category.
The C locale is used if none of these environment variables are set, if the locale
catalog is not installed, or if grep was not compiled with national language support
(NLS). The shell command locale -a lists locales that are currently available.

GREP_COLOR
This variable specifies the color used to highlight matched (non-empty) text.
It is deprecated in favor of GREP_COLORS, but still supported. The mt, ms,
and mc capabilities of GREP_COLORS have priority over it. It can only specify
the color used to highlight the matching non-empty text in any matching line
(a selected line when the -v command-line option is omitted, or a context line
when -v is specified). The default is 01;31, which means a bold red
foreground text on the terminal's default background.

GREP_COLORS
Specifies the colors and other attributes used to highlight various parts of
the output. Its value is a colon-separated list of capabilities that defaults
to ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36 with the rv and ne
boolean capabilities omitted (i.e., false). Supported capabilities are as
follows.

sl= SGR substring for whole selected lines (i.e., matching lines when the
-v command-line option is omitted, or non-matching lines when -v is
specified). If however the boolean rv capability and the -v command-
line option are both specified, it applies to context matching lines
instead. The default is empty (i.e., the terminal's default color
pair).

cx= SGR substring for whole context lines (i.e., non-matching lines when
the -v command-line option is omitted, or matching lines when -v is
specified). If however the boolean rv capability and the -v command-
line option are both specified, it applies to selected non-matching
lines instead. The default is empty (i.e., the terminal's default
color pair).

rv Boolean value that reverses (swaps) the meanings of the sl= and cx=
capabilities when the -v command-line option is specified. The default
is false (i.e., the capability is omitted).

mt=01;31
SGR substring for matching non-empty text in any matching line (i.e., a
selected line when the -v command-line option is omitted, or a context
line when -v is specified). Setting this is equivalent to setting both
ms= and mc= at once to the same value. The default is a bold red text
foreground over the current line background.

ms=01;31
SGR substring for matching non-empty text in a selected line. (This is
only used when the -v command-line option is omitted.) The effect of
the sl= (or cx= if rv) capability remains active when this kicks in.
The default is a bold red text foreground over the current line
background.

mc=01;31
SGR substring for matching non-empty text in a context line. (This is
only used when the -v command-line option is specified.) The effect of
the cx= (or sl= if rv) capability remains active when this kicks in.
The default is a bold red text foreground over the current line
background.

fn=35 SGR substring for file names prefixing any content line. The default
is a magenta text foreground over the terminal's default background.

ln=32 SGR substring for line numbers prefixing any content line. The default
is a green text foreground over the terminal's default background.

bn=32 SGR substring for byte offsets prefixing any content line. The default
is a green text foreground over the terminal's default background.

se=36 SGR substring for separators that are inserted between selected line
fields (:), between context line fields, (-), and between groups of
adjacent lines when nonzero context is specified (--). The default is
a cyan text foreground over the terminal's default background.

ne Boolean value that prevents clearing to the end of line using Erase in
Line (EL) to Right (33[K) each time a colorized item ends. This is
needed on terminals on which EL is not supported. It is otherwise
useful on terminals for which the back_color_erase (bce) boolean
terminfo capability does not apply, when the chosen highlight colors do
not affect the background, or when EL is too slow or causes too much
flicker. The default is false (i.e., the capability is omitted).

Note that boolean capabilities have no =... part. They are omitted (i.e.,
false) by default and become true when specified.

See the Select Graphic Rendition (SGR) section in the documentation of the
text terminal that is used for permitted values and their meaning as character
attributes. These substring values are integers in decimal representation and
can be concatenated with semicolons. grep takes care of assembling the result
into a complete SGR sequence (33[...m). Common values to concatenate include
1 for bold, 4 for underline, 5 for blink, 7 for inverse, 39 for default
foreground color, 30 to 37 for foreground colors, 90 to 97 for 16-color mode
foreground colors, 38;5;0 to 38;5;255 for 88-color and 256-color modes
foreground colors, 49 for default background color, 40 to 47 for background
colors, 100 to 107 for 16-color mode background colors, and 48;5;0 to 48;5;255
for 88-color and 256-color modes background colors.

LC_ALL, LC_COLLATE, LANG
These variables specify the locale for the LC_COLLATE category, which
determines the collating sequence used to interpret range expressions like
[a-z].

LC_ALL, LC_CTYPE, LANG
These variables specify the locale for the LC_CTYPE category, which determines
the type of characters, e.g., which characters are whitespace. This category
also determines the character encoding, that is, whether text is encoded in
UTF-8, ASCII, or some other encoding. In the C or POSIX locale, all
characters are encoded as a single byte and every byte is a valid character.

LC_ALL, LC_MESSAGES, LANG
These variables specify the locale for the LC_MESSAGES category, which
determines the language that grep uses for messages. The default C locale
uses American English messages.

POSIXLY_CORRECT
If set, grep behaves as POSIX requires; otherwise, grep behaves more like
other GNU programs. POSIX 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 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.

NOTES
This man page is maintained only fitfully; the full documentation is often more up-
to-date.

This is free software; see the source for copying conditions. There is NO warranty;
not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

BUGS
Reporting Bugs
Email bug reports to the bug-reporting address [email protected]?. An email archive
?https://lists.gnu.org/mailman/listinfo/bug-grep? and a bug tracker
?https://debbugs.gnu.org/cgi/pkgreport.cgi?package=grep? are available.

Known Bugs
Large repetition counts in the {n,m} 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.

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

EXAMPLE
The following example outputs the location and contents of any line containing “f”
and ending in “.c”, within all files in the current directory whose names contain “g”
and end in “.h”. The -n option outputs line numbers, the -- argument treats expan‐
sions of “*g*.h” starting with “-” as file names not options, and the empty file
/dev/null causes file names to be output even if only one file name happens to be of
the form “*g*.h”.

$ grep -n -- 'f.*.c$' *g*.h /dev/null
argmatch.h:1:/* definitions and prototypes for argmatch.c

The only line that matches is line 1 of argmatch.h. Note that the regular expression
syntax used in the pattern differs from the globbing syntax that the shell uses to
match file names.

SEE ALSO
Regular Manual Pages
awk(1), cmp(1), diff(1), find(1), perl(1), sed(1), sort(1), xargs(1), read(2),
pcre(3), pcresyntax(3), pcrepattern(3), terminfo(5), glob(7), regex(7).

Full Documentation
A complete manual ?https://www.gnu.org/software/grep/manual/? is available. If the
info and grep programs are properly installed at your site, the command

info grep

should give you access to the complete manual.

GNU grep 3.6 2019-12-29 GREP(1)