======== 尖括號^ :例：^work:表示以work開頭的內容
======== $: work$: 表示以work結尾的內容
======== ^$:表示空行，不是空格
======== . 代表且只能代表任意一個字符
======== \ 代表轉意字符（讓代表特殊意義的字符返回原形）例子： \.:只表示小數點
======== * 重復0個或者多個前面的字符，不代表所有了
======== .* 匹配所有的字符。
======== ^.* 任意多個字符開頭
======== [abc] 匹配字符集內任意一個字符
======== [a-z] 匹配任意字符
======== [^abc]尖括號在中括號裡面表示非
======== ｛n，m｝重復n到m次
======== ｛n，｝至少n次，多了不限
======== ｛n｝次
======== ｛，m｝最頂m次；注不行，改為｛0，m｝
grep常用命令：
-v 排除匹配的內容
-E 支持擴展的正則表達式
-i 忽略大小寫
-o 只輸出匹配內容
--color=auto 匹配的內容顯示顏色
-n 在行首顯示行號
終端輸入：man grep（全部參數如下）
OPTIONS
Generic Program Information
--help Print a usage message briefly summarizing these 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 (see below).
Matcher Selection
-E, --extended-regexp
Interpret PATTERN as an extended regular expression (ERE, see below). (-E is specified by POSIX.)
-F, --fixed-strings
Interpret PATTERN as a list of fixed strings, separated by newlines, any of which is to be matched. (-F is specified by POSIX.)
-G, --basic-regexp
Interpret PATTERN as a basic regular expression (BRE, see below). This is the default.
-P, --perl-regexp
Interpret PATTERN as a Perl regular expression. This is highly experimental and grep -P may warn of unimplemented features.
Matching Control
-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? -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 (--) between contiguous groups of matches. With the -o
or --only-matching option, this has no effect and a warning is given.
-B NUM, --before-context=NUM
Print NUM lines of leading context before matching lines. Places a line containing a group separator (--) between contiguous groups of matches. With the -o
or --only-matching option, this has no effect and a warning is given.
-C NUM, -NUM, --context=NUM
Print NUM lines of output context. Places a line containing a group separator (--) between contiguous groups of matches. With the -o or --only-matching
option, this has no effect and a warning is given.
File and Directory Selection
-a, --text
Process a binary file as if it were text; this is equivalent to the --binary-files=text option.
--binary-files=TYPE
If 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, which means that directories are read just as if they were ordinary
files. 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.
--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, -r, --recursive
Read all files under each directory, recursively; this is equivalent to the -d recurse option.
Other Options
--line-buffered
Use line buffering on output. This can cause a performance penalty.
--mmap If possible, use the mmap(2) system call to read input, instead of the default read(2) 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.
-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.
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