Linux Learning notes-Regular expressions

&& and success-execution unsuccessful-do not execute

|| or success-not performing unsuccessful-execution

; (not) Success-execution

grep--color ' root '/etc/passwd highlight

echo "Alias cg= ' grep--clort '" >> ~/.BASHRC

-N Display number of rows

-C counts a few rows

-V does not contain keyword

-A 2 shows the next two lines

-B More than 2 shows the last two lines

-C 2 more display the upper and lower lines

-R ' root '/etc/* directory search keywords, with file directory name, content

-RH does not show the front directory path

CG ' [0-9] ' 1.txt

CG ' [a-za-z] ' 1.txt

Cg-v ' [a-za-z] ' 1.txt does not contain

CG ' ^[a-z] ' 1.txt starts with a letter

CG ' [^0-9] ' 1.txt does not contain a pure number, does not contain a blank line

CG ' ^[^0-9] ' 1.txt lines that do not start with a number, do not contain blank lines

CG ' ^$ ' 1.txt show Blank line

CG ' R.O ' 1.txt any one character

CG ' R*o ' 1.txt 0 or more front character O also conforms to

CG ' R.*o ' 1.txt r start O results count, no matter what in the middle

CG ' R\?o ' 1.txt de-semantic characters ==cg-e ' r?o ' 0 or 1 preceding characters

GREP-E ==egrep E instead of de-righteousness

Egrep ' R+o ' 1.txt 1 or more preceding characters

+ ? () {} | need to use EGREP or grep-e or de-righteousness \

Egrep ' Root|nologin ' 1.txt or

grep ' Root ' 1.txt | grep ' Nologin ' and

Egrep ' (RR) + ' 1.txt overall match ==grep-e ' (RR) + ' 1.txt

Egrep ' (RR) {1,3} ' 1.txt matches 1 to 3 times

Egrep ' (RR) {5} ' 1.txt matches 5 times

SED differs from grep with no support for color grep all features sed support

Display function, n r//P

Sed-n ' P 1.txt print first 10 lines ' 1,10 ' 3,$ '

Sed-n '/root/' P 1.txt contains the root row

Sed-n '/r.ot/' P 1.txt '/r*o/'/r.*o/'

Sed-n '/r\?ot/' P 1.txt '/r\+o/'/root\|nologin/'/\ (oo\) \+/'

Sed-n '/root/p; /mail/p ' passwd show root or mail line, all contained, display multiple times

= = = Sed-n-E '/root/p '-e '/mail/p ' passwd encounter an order

Sed-n-R '/root|mail/p ' passwd will not be displayed multiple times

R instead of de-justification

Sed-r-n '/(OO) +/' P 1.txt no need to be de-justified

'/[0-9]/'/[^0-9]/' pure number '/[^a-za-z]/' pure letter '/^$/' empty line

Delete function, no need to de-justification and R, keyword required//, no keywords do not need///

Sed '/^$/' d 1.txt Delete empty line '/[0-9]/'/[a-za-z]/'

Sed ' 1,19 ' d 1.txt Delete 1 to 19 rows does not change file contents

Sed-i ' 1,19 ' d 1.txt change file contents wc-l 1.txt not recommended, preview before use, or CP

Find and replace, similar to Vim, @#

Sed ' 1,10s/nologin/login/g ' 1.txt 1 to 10 lines replace-I directly modify content

Sed ' 1,10s/\/sbin\/login/login/g ' 1.txt de-righteousness

Sed ' 1,10s#/sbin/login#login#g ' 1.txt no need to be de-justified

Sed ' 1,[email protected]/sbin/[email protected]@g ' 1.txt no need to de-righteousness

Sed ' [email protected]/sbin/[email protected]@g ' 1.txt Replace All

Sed ' [email protected]^.*[email protected]@g ' 1.txt all lines replaced by & for a full line

Sed ' [email protected]^.*[email protected]&[email protected] ' all line endings added

Sed ' [email protected]^.*[email protected]& [email protected] ' more spaces

Sed ' s#[0-9]# #g ' Delete all numbers, empty [a-za-z]

Sed ' s#[^0-9a-za-z]# #g ' remove all special characters

Change

Sed-r ' 1,10s# (^[a-za-z0-9]+) (:. *:) (. *$) #\3\2\1#g ' first and last swap positions, not including special symbols

Sed-r ' s/(^.) (.*) (. $)/\3\2\1/g ' passwd first word and last character swap

awk difference segment does not support color, {} grep sed support {} is not supported

Show

Awk-f ': ' ofs= ': ' {print $3,$4} ' passwd OFS specify delimiter

The

awk '/root/' passwd

awk '/root|user/' passwd or, will not be displayed more than once, no need to de-justification

awk '/r*o/' passwd. *. ? +

awk '/(OO) +/' passwd

Awk-f ': ' $1~/r*o/' passwd segment match

Awk-f ': ' $1~/r*o/{print $} ' passwd only shows a segment after matching

Awk-f ': ' $1~/r*o/{print $}; $1~/mail/{print '} ' passwd or, multiple, multi-display

Awk-f ': ' $1~/r*o|mail/{print '} ' passwd, but will not be displayed more than once

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Linux Learning notes-Regular expressions