官方文档：grep 命令

2 Invoking grep

The general synopsis of the grep command line is

There can be zero or more option arguments, and zero or more file arguments. The patterns argument contains one or more patterns separated by newlines, and is omitted when patterns are given via the ‘-e patterns’ or ‘-f file’ options. Typically patterns should be quoted when grep is used in a shell command.

2.1 Command-line Options

grep comes with a rich set of options: some from POSIX and some being GNU extensions. Long option names are always a GNU extension, even for options that are from POSIX specifications. Options that are specified by POSIX, under their short names, are explicitly marked as such to facilitate POSIX-portable programming. A few option names are provided for compatibility with older or more exotic implementations.

Several additional options control which variant of the grep matching engine is used. See grep Programs.

• Generic Program Information
• Matching Control
• General Output Control
• Output Line Prefix Control
• Context Line Control
• File and Directory Selection
• Other Options

2.1.1 Generic Program Information

–help

Print a usage message briefly summarizing the command-line options and the bug-reporting address, then exit.

-V–version

Print the version number of grep to the standard output stream. This version number should be included in all bug reports.

2.1.2 Matching Control

-e patterns–regexp=patterns

Use patterns as one or more patterns; newlines within patterns separate each pattern from the next. If this option is used multiple times or is combined with the -f (–file) option, search for all patterns given. Typically patterns should be quoted when grep is used in a shell command. (-e is specified by POSIX.)

-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. (-f is specified by POSIX.)

-i-y–ignore-case

Ignore case distinctions in patterns and input data, so that characters that differ only in case match each other. Although this is straightforward when letters differ in case only via lowercase-uppercase pairs, the behavior is unspecified in other situations. For example, uppercase “S” has an unusual lowercase counterpart “ſ” (Unicode character U+017F, LATIN SMALL LETTER LONG S) in many locales, and it is unspecified whether this unusual character matches “S” or “s” even though uppercasing it yields “S”. Another example: the lowercase German letter “ß” (U+00DF, LATIN SMALL LETTER SHARP S) is normally capitalized as the two-character string “SS” but it does not match “SS”, and it might not match the uppercase letter “ẞ” (U+1E9E, LATIN CAPITAL LETTER SHARP S) even though lowercasing the latter yields the former.

-y is an obsolete synonym that is provided for compatibility. (-i is specified by POSIX.)

–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, in order to cancel its effects because the two options override each other.

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

Because the -w option can match a substring that does not begin and end with word constituents, it differs from surrounding a regular expression with ‘\

-x–line-regexp

Select only those matches that exactly match the whole line. For regular expression patterns, this is like parenthesizing each pattern and then surrounding it with ‘^’ and ‘$’. (-x is specified by POSIX.)

2.1.3 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, 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 and default to ‘ms=01;31:mc=01;31:sl=:cx=:fn=35:ln=32:bn=32:se=36’ for bold red matched text, magenta file names, green line numbers, green byte offsets, cyan separators, and default terminal colors otherwise. The deprecated environment variable GREP_COLOR is still supported, but its setting does not have priority; it defaults to ’01;31′ (bold red) which only covers the color for matched text. 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.

-l–files-with-matches

Suppress normal output; instead print the name of each input file from which output would normally have been printed. Scanning each input file stops upon first match. (-l is specified by POSIX.)

-m num–max-count=num

Stop after the first num selected lines. If the input is standard input from a regular file, and num selected lines are output, grep ensures that the standard input is positioned just after the last selected line before exiting, regardless of the presence of trailing context lines. This enables a calling process to resume a search. For example, the following shell script makes use of it:

while grep -m 1 'PATTERN'
do
  echo xxxx
done < FILE

But the following probably will not work because a pipe is not a regular file:

This probably will not work.

cat FILE |
while grep -m 1 'PATTERN'
do
  echo xxxx
done

When grep stops after num selected 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 matching lines, with each such part on a separate output line. Output lines use the same delimiters as input, and delimiters are null bytes if -z (–null-data) is also used (see Other Options).

-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. 1 USG-style grep also lacked -q but its -s option behaved like GNU grep‘s. 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.)

2.1.4 Output Line Prefix Control

When several prefix fields are to be output, the order is always file name, line number, and byte offset, regardless of the order in which these options were specified.

-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'

-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. This may also prepend spaces to output line numbers and byte offsets so that lines from a single file all start at the same column.

-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.

2.1.5 Context Line Control

Context lines are non-matching lines that are near a matching line. They are output only if one of the following options are used. Regardless of how these options are set, grep never outputs any given line more than once. If the -o (–only-matching) option is specified, these options have no effect and a warning is given upon their use.

-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-num–context=num

Print num lines of leading and trailing output context.

–group-separator=string

When -A, -B or -C are in use, print string instead of — between groups of lines.

–no-group-separator

When -A, -B or -C are in use, do not print a separator between groups of lines.

Here are some points about how grep chooses the separator to print between prefix fields and line content:

• Matching lines normally use ‘:’ as a separator between prefix fields and actual line content.

• Context (i.e., non-matching) lines use ‘-‘ instead.

• When context is not specified, matching lines are simply output one right after another.

• When context is specified, lines that are adjacent in the input form a group and are output one right after another, while by default a separator appears between non-adjacent groups.

• The default separator is a ‘–‘ line; its presence and appearance can be changed with the options above.

• Each group may contain several matching lines when they are close enough to each other that two adjacent groups connect and can merge into a single contiguous one.

2.1.6 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 (see Environment Variables), or null input bytes when the -z (–null-data) option is not given (see Other Options).

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 binary data 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 (–null-data) 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 (–binary-files=text) 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. If action is ‘read’, all devices are read just as if they were ordinary files. If action is ‘skip’, devices, FIFOs, and sockets are silently skipped. By default, devices are read if they are on the command line or if the -R (–dereference-recursive) option is used, and are skipped if they are encountered recursively and the -r (–recursive) option is used. This option has no effect on a file that is read via standard input.

-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 file systems disallow this, and will cause grep to print error messages for every directory or silently skip them). If action is ‘skip’, directories are silently skipped. If action is ‘recurse’, grep reads all files under each directory, recursively, following command-line symbolic links and skipping other symlinks; 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 name matches any of the patterns 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 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

For each directory operand, read and process all files in that directory, recursively. Follow symbolic links on the command line, but skip symlinks that are encountered recursively. Note that if no file operand is given, grep searches the working directory. This is the same as the ‘–directories=recurse’ option.

-R–dereference-recursive

For each directory operand, read and process all files in that directory, recursively, following all symbolic links.

2.1.7 Other Options

—

Delimit the option list. Later arguments, if any, are treated as operands even if they begin with ‘-‘. For example, ‘grep PAT — -file1 file2’ searches for the pattern PAT in the files named -file1 and file2.

–line-buffered

Use line buffering for standard output, regardless of output device. By default, standard output is line buffered for interactive devices, and is fully buffered otherwise. With full buffering, the output buffer is flushed when full; with line buffering, the buffer is also flushed after every output line. The buffer size is system dependent.

-U–binary

On platforms that distinguish between text and binary I/O, use the latter when reading and writing files other than the user’s terminal, so that all input bytes are read and written as-is. This overrides the default behavior where grep follows the operating system’s advice whether to use text or binary I/O. On MS-Windows when grep uses text I/O it reads a carriage return–newline pair as a newline and a Control-Z as end-of-file, and it writes a newline as a carriage return–newline pair.

When using text I/O –byte-offset (-b) counts and –binary-files heuristics apply to input data after text-I/O processing. Also, the –binary-files heuristics need not agree with the –binary option; that is, they may treat the data as text even if –binary is given, or vice versa. See File and Directory Selection.

This option has no effect on GNU and other POSIX-compatible platforms, which do not distinguish text from binary I/O.

-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.

2.2 Environment Variables

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

The locale for category <span class="nolinebreak">LC_foo</span> is specified by examining the three environment variables LC_ALL, <span class="nolinebreak">LC_foo</span>, and 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_COLLATE is set to ‘pt_BR’, then the Brazilian Portuguese locale is used for the LC_COLLATE category. As a special case for LC_MESSAGES only, the environment variable LANGUAGE can contain a colon-separated list of languages that overrides the three environment variables that ordinarily specify 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.

Many of the environment variables in the following list let you control highlighting using Select Graphic Rendition (SGR) commands interpreted by the terminal or terminal emulator. (See the section in the documentation of your text terminal for permitted values and their meanings 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.

The two-letter names used in the GREP_COLORS environment variable (and some of the others) refer to terminal “capabilities,” the ability of a terminal to highlight text, or change its color, and so on. These capabilities are stored in an online database and accessed by the terminfo library. 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

This variable specifies the colors and other attributes used to highlight various parts of the output. Its value is a colon-separated list of terminfo 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 used only when the -v command-line option is omitted.) The effect of the ‘sl=’ (or ‘cx=’ if ‘rv’) capability remains active when this takes effect. 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 used only when the -v command-line option is specified.) The effect of the ‘cx=’ (or ‘sl=’ if ‘rv’) capability remains active when this takes effect. 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. LC_ALL LC_COLLATE LANG

These variables specify the locale for the LC_COLLATE category, which might affect how range expressions like ‘[a-z]’ are interpreted. 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. See Character Encoding. LANGUAGE 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, POSIXLY_CORRECT disables special handling of an invalid bracket expression. See invalid-bracket-expr. _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.

The GREP_OPTIONS environment variable of grep 2.20 and earlier is no longer supported, as it caused problems when writing portable scripts. To make arbitrary changes to how grep works, you can use an alias or script instead. For example, if grep is in the directory ‘/usr/bin’ you can prepend $HOME/bin to your PATH and create an executable script $HOME/bin/grep containing the following:

#! /bin/sh
export PATH=/usr/bin
exec grep --color=auto --devices=skip "$@"

Original: https://www.cnblogs.com/onelikeone/p/16414097.html
Author: 行走的思想
Title: 官方文档：grep 命令