码迷,mamicode.com
首页 > 系统相关 > 详细

linux 正则表达式基础篇

时间:2016-06-30 23:48:47      阅读:413      评论:0      收藏:0      [点我收藏+]

标签:linux   表达式   小数点   color   

========  尖括号^ :例:^work:表示以work开头的内容
========  $:            work$: 表示以work结尾的内容

========  ^$:表示空行,不是空格

========  . 代表且只能代表任意一个字符
========  \ 代表转意字符(让代表特殊意义的字符返回原形)例子: \.:只表示小数点
========  * 重复0个或者多个前面的字符,不代表所有了
========  .* 匹配所有的字符。
========  ^.* 任意多个字符开头

========  [abc] 匹配字符集内任意一个字符
========  [a-z] 匹配任意字符
========  [^abc]尖括号在中括号里面表示非

========  {n,m}重复n到m次
========  {n,}至少n次,多了不限
========  {n}次
========  {,m}最顶m次;注不行,改为{0,m}

grep常用命令:
-v 排除匹配的内容
-E 支持扩展的正则表达式
-i 忽略大小写
-o 只输出匹配内容
--color=auto 匹配的内容显示颜色
-n 在行首显示行号

终端输入:man grep(全部参数如下)

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.

本文出自 “一起来吧” 博客,谢绝转载!

linux 正则表达式基础篇

标签:linux   表达式   小数点   color   

原文地址:http://daxionglaiba.blog.51cto.com/11790757/1794580

(0)
(0)
   
举报
评论 一句话评论(0
登录后才能评论!
© 2014 mamicode.com 版权所有  联系我们:gaon5@hotmail.com
迷上了代码!