Three Musketeers: grep sed awk
grep: text line filtering tools
sed: text line editor (stream editor)
awk: report generator, an output formatter
grep contains three commands:
grep egrep fgrep. They are used for pattern matching row
egrep: = grep -E uses extended regular expressions to match
fgrep = fast grep only files matching a wildcard
* Grep default use regular expressions to match text
grep usage:
grep [option] …PATTERN [filename]
grep common options:
| -E |
Supports extended regular expressions |
| -P |
Using perl regular expression language search engine (each language) |
| -I |
Ignore case |
| -O |
Only output matching content (the default output is a row) |
| -v |
Anti-election |
| --color=auto |
Syntax coloring |
| -n |
Show Line Numbers |
pattern-- regular expression:
Role: through some special characters to represent a class character, and then to the front of the command to execute. If you are using a special meaning in itself, it is necessary \ to escape.
1. Character Matches:
Any of a character?
[] Any one of the characters in the range
Any one character [^] outside the range
字符类：[:digit:] [:alnum:] [:alpha:] [:lower:] [:upper:] [:space:] [:punct:]
2. The number of matches
* Match preceding character zero to n times
\? Matches the preceding character zero to 1
Matches the preceding character + 1 to n times
\ {M \} matches foregoing character m times
\ {M, n \} matches the character preceding to n times m
\ {0, n \} Matches the preceding character 0 to n times
\ {M, \} the preceding matching character least m
3. The position of the anchor
^ Anchor of the line
$ Anchored end of the line
\ B anchor and anchor the first word endings
\> Anchor suffix
<\ Anchoring the first word
4. Packet
abc * abccccc abc we want as a whole
\ (\) Example: \ (abc \) * abcabcabc abcccc
** grouping characteristics: By default, linux packet will specify the variable representation variables ,, \ 1 \ 2 \ 3 ............
(((2(5[0-5]|[0-4]\d))|[0-1]?\d{1,2})(\.((2(5[0-5]|[0-4]\d))|[0-1]?\d{1,2})){3})