Linux grep command

grep
NAME
grep, egrep, fgrep - print lines matching a pattern 打印匹配模式的行

SYNOPSIS
grep [OPTIONS] PATTERN [FILE…]
grep [OPTIONS] [-e PATTERN | -f FILE] [FILE…]

DESCRIPTION
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
grep 用于在输入的文件中查找包含给定的匹配模式的行
PATTERN. By default, grep prints the matching lines.
模式，默认打印匹配的行
In addition, two variant programs egrep and fgrep are available. egrep is the same as grep -E. fgrep is the same as grep -F. Direct invocation as either egrep or fgrep is
另外，它用两个可用的变体的程序egrep和fgrep。egrep 等同于grep -E 。fgrep 等同于grep -F。 你要么直接调用egrep或fgrep
deprecated, but is provided to allow historical applications that rely on them to run unmodified.

OPTIONS
Generic Program Information通用程序信息
–help Print a usage message briefly summarizing these command-line options and the bug-reporting address, then exit.
打印使用信息，简要的命令行选项和bug反馈地址然后退出
-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).
打印grep的版本号到标准输出流，这个版本号需要包含在反馈的所有bug
Matcher Selection匹配选择
-E, –extended-regexp扩展的正则
Interpret PATTERN as an extended regular expression (ERE, see below). (-E is specified by POSIX.)
使用扩展的正则表达式解释模式
-F, –fixed-strings, –fixed-regexp
Interpret PATTERN as a list of fixed strings, separated by newlines, any of which is to be matched. (-F is specified by POSIX, –fixed-regexp is an obsoleted alias, please
do not use it in new scripts.)
-G, –basic-regexp基本的正则
Interpret PATTERN as a basic regular expression (BRE, see below). This is the default
基本的正则表达式解释模式，这个是默认值
-P, –perl-regexp perl类型的正则
Interpret PATTERN as a Perl regular expression. This is highly experimental and grep -P may warn of unimplemented features.
perl正则表达式解释模式，这是高度实验和grep -p可以警告未实现的功能
Matching Control匹配控制
-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.)

   -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.)   -i, --ignore-case          Ignore case distinctions in both the PATTERN and the input files.  (-i is specified by POSIX.)   -v, --invert-match          Invert the sense of matching, to select non-matching lines.  (-v is specified by POSIX.)   -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.   -x, --line-regexp          Select only those matches that exactly match the whole line.  (-x is specified by POSIX.)   -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. (-c is
specified by POSIX.)

   --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.  (-l is          specified by POSIX.)   -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.  (-q is specified by POSIX.)   -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.)

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.  (-n is specified by POSIX.)   -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 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.   -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 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.   --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=DIR          Exclude directories matching the pattern DIR from recursive searches.   -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.  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 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.   -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.

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,” “extended” and “perl.” 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  regular  expressions  give  additional  functionality,  and  are  documented  in  pcresyntax(3)  and   pcrepattern(3), but may not be available on every 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.

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. 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:],   [: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 \b 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 \n, 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 ).

   Traditional  egrep  did  not support the { meta-character, and some egrep implementations support \{ instead, so portable scripts should avoid { in grep -E patterns and should use   [{] to match a literal {.   GNU grep -E attempts to support traditional usage by assuming that { is not special if it would be the start of an  invalid  interval  specification.   For  example,  the  command   grep -E '{1'  searches  for  the  two-character  string {1 instead of reporting a syntax error in the regular expression.  POSIX allows this behavior as an extension, but portable   scripts should avoid it.

ENVIRONMENT VARIABLES
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).   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.   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.   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.

EXIT STATUS
Normally, the exit status is 0 if selected lines are found and 1 otherwise. But the exit status is 2 if an error occurred, unless the -q or –quiet or –silent option is used and
a selected line is found. Note, however, that POSIX only mandates, for programs such as grep, cmp, and diff, that the exit status in case of error be greater than 1; it is
therefore advisable, for the sake of portability, to use logic that tests for this general condition instead of strict equality with 2.

COPYRIGHT
Copyright 1998-2000, 2002, 2005-2014 Free Software Foundation, Inc.

   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 [e-mail], a mailing list whose web page is http://lists.gnu.org/mailman/listinfo/bug-grep. grep’s Savannah bug tracker is located at
http://savannah.gnu.org/bugs/?group=grep.

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.

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

POSIX Programmer’s Manual Page
grep(1p).

TeXinfo Documentation
The full documentation for grep is maintained as a TeXinfo manual, which you can read at http://www.gnu.org/software/grep/manual/. If the info and grep programs are properly
installed at your site, the command

          info grep   should give you access to the complete manual.

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

   GNU's not Unix, but Unix is a beast; its plural form is Unixen.

User Commands GNU grep 2.20 GREP(1)