Summary of implementation of string interception method under Linux

The implementation of string interception under Linux can be broadly divided into two types, using commands to intercept, and using tools for interception. The specific interception methods are as follows:

A, #截取, can be implemented to delete the left character, retain the right character

Delete </> and all previous characters from the first </> on the left

Str=http://www.baidu.com/index.htmlecho ${str#*/} # Right First/output:/www.baidu.com/index.html

B, # #截取, you can delete the left character, leave the right character

Delete </> and all previous characters from the far right </> start

Str=http://www.baidu.com/index.htmlecho ${str##*/} # rightest/output: index.html

C,% intercept, can be implemented to delete the right character, leaving the left character

Delete </> and all characters to the right from the first </> on the right

Str=http://www.baidu.com/index.htmlecho ${str%/*} # Left Firft/output: http://www.baidu.com

d, Percent intercept, you can delete the right character, leave the left character

Delete </> and all characters to the right from the first </> on the left

Str=http://www.baidu.com/index.htmlecho ${str%%/*} # leftest/output: http:

e, interval interception

Intercept the No. 0 to 6th character

Str=http://www.baidu.com/index.htmlecho ${str:0:6} output: http:/

F, forward interval intercept to end

Intercept starts from 7th character to end

Str=http://www.baidu.com/index.htmlecho ${str:7} output: www.baidu.com/index.html

g, reverse interval intercept

Intercept the top 5 of the No. 0 to 7th characters

Str=http://www.baidu.com/index.htmlecho ${str:0-7:5} output: ex.ht

h, Reverse intercept, to the end

Intercept from the last 10th character to the end of the string

Str=http://www.baidu.com/index.htmlecho ${str:0-10} output: index.html

I, using the Cut command to implement string interception

Cut [Options] Options:-B----> byte-c----> character-f----> domain created a file with the following contents: [ [email protected] 3_26]$ cat FILEABCDEFG1234567POIUYTR

Examples of using cut interception are as follows:

[email protected] 3_26]$ Cat File | Cut-b 3c3i[[email protected] 3_26]$ cat File | Cut-b -3abc123poi[[email protected] 3_26]$ cat File | Cut-b 3-cdefg34567iuytr[[email protected] 3_26]$ cat File | Cut-b 3-5cde345iuy[[email protected] 3_26]$ cat File | Cut-b 3-5,7cdeg3457iuyr

For single-byte,-B and-C seem to work the same, but if the text appears in the case of Chinese,-C is able to correctly output a Chinese character, but using the-B option output is garbled, because a Chinese is two bytes. To solve this problem, the-B option is usually used with the-n option, and-n is used to tell the cut to intercept N-byte characters.

The following explains the role of domain <-f>. All the user information is saved in the/etc/passwd file, and you can see that each long string is separated by: We can assume that the data in the file is delimited by: separate domains. Specifies that the domain delimiter uses the-D option, followed by-F with a number format that is exactly the same as-B. "Cut's field delimiter can only be one character"

[Email protected] 3_26]$ CAT/ETC/PASSWD | Head-n 5root:x:0:0:root:/root:/bin/bashbin:x:1:1:bin:/bin:/sbin/nologindaemon:x:2:2:daemon:/sbin:/sbin/ Nologinadm:x:3:4:adm:/var/adm:/sbin/nologinlp:x:4:7:lp:/var/spool/lpd:/sbin/nologin[[email protected] 3_26]$ CAT/ etc/passwd | Head-n 5 | Cut-d:-F 1ROOTBINDAEMONADMLP

Needless to say, look at the following example

[[Email protected] 3_26]$ PS PID TTY time CMD 5630 pts/2 00:00:00 bash 5739 pts/2 00:00:00 ps[[email prote CTED] 3_26]$ PS | Cut-b 4i344

Obviously only three lines, but cut out four lines of content, because each command is actually a parent bash created alone a process, cut is no exception (built-in command).

-----Muhuizz Finishing

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Summary of implementation of string interception method under Linux