Extended usage of Text Processing command series--grep

Regular expressions are divided into basic regular expressions and extended regular expressions.

Typically, grep uses a basic regular expression, and if you want to use an extended regular expression, you can use the-e option, which is equivalent to Egrep

Some other options for grep:

-A N: Displays the n rows after the matching line, (after).

-B N: Displays the n rows preceding the matching line, (before).

-C N: Displays the front and back n rows. (context)

Example 1:

[[email protected] tmp]# grep--color-a 1 ' ^cpu MHz '/proc/cpuinfocpu mhz:2392.390cache size:3072 kb[[em AIL protected] tmp]#

[[email protected] tmp]# grep --color -a 1 -b 2  ' ^cpu MHz '  /proc/cpuinfomodel name      : intel (R)  Core (TM)   i3-2370m cpu @ 2.40ghzstepping        : 7cpu  mhz         : 2392.390cache size       : 3072 kb[[email protected] tmp]#[[email protected] tmp]#  grep --color -C 2  ' ^cpu mhz '  /proc/cpuinfomodel name       : intel (R)  core (TM)  i3-2370M CPU @ 2.40GHzstepping         : 7cpu MHz          : 2392.390cache size      : 3072 kbfpu : yes [[Email protected] tmp]# 

An extended regular expression:

In the extended regular expression inside the metacharacters and basic regular expressions inside the meta-characters are basically the same, the difference is mainly a few:

+: Matches the previous character appears 1 or more times.

{N,m}: The previous character appears N to M times.

|: Represents or. If a|b, the match is either A or B.

(): Indicates grouping, no backslash is required.

[[email protected] tmp]# grep-e ' (c|c) at ' Aacatcat[[email protected] tmp]#

Matches the number between 1-255:

Grep-e--color ' \b ([0-9]|[ 1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5]) \b '




[Email protected] ~]# Ifconfig bond0 | grep ' inet addr ' | Grep-e--color-o ' (\b ([0-9]|[ 1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5]) (\.\b) {3}\b ([0-9]|[ 1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5]) \b ' 172.17.100.252172.17.100.255255.255.255.0[[email protected] ~]#

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Extended usage of Text Processing command series--grep