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This article mainly introduces how to use awk in linux. It is very detailed and has a certain reference value. Friends who are interested must finish it!

1. Intercept a segment in a document

The example commands are as follows:

# head-N2 test.txt | awk-F':'{print $1} 'rootbin

In this case, the-F option specifies the delimiter. If the-F option is not added, spaces or tab are used as delimiters. Print is the act of printing, used to print a field. $1 is the 1st field, $2 is the 2nd field, and so on. However, $0 is special in that it represents the entire line:

# head-N2 test.txt | awk-favored root:x:0:0:root:/root:/bin/bashbin:x:1:1:bin:/bin:/sbin/nologin'{print $0} 'root:x:0:0:root:/root:/bin/bashbin:x:1:1:bin:/bin:/sbin/nologin

Note the format of awk.-F is followed by single quotation marks, which are delimited. The actions of print should be enclosed in {}, otherwise an error will be reported. Print can also print customized content, but the customized content should be enclosed in double quotes, as shown below:

# head-N2 test.txt | awk-F':'{print $1 "#" $2 "#" $3 "#" $4} 'root#x#0#0bin#x#1#12. Match character or string

Filter out the lines containing the specified string in the document. The example command is as follows:

# awk'/ oo/' test.txtroot:x:0:0:root:/root:/bin/bashlp:x:4:7:lp:/var/spool/lpd:/sbin/nologinmail:x:8:12:mail:/var/spool/mail:/sbin/nologinoperator:x:11:0:operator:/root:/sbin/nologinpostfix:x:89:89::/var/spool/postfix:/sbin/nologinsetroubleshoot:x:992:990::/var/lib/setroubleshoot:/sbin/nologin

This is similar to the use of sed, can achieve the function of grep, but there is no color display, certainly not as easy to use as grep. However, awk has a more powerful match than sed, as shown below:

# awk-F':'$1 ~ / oo/' test.txtroot:x:0:0:root:/root:/bin/bashsetroubleshoot:x:992:990::/var/lib/setroubleshoot:/sbin/nologin

It can let a certain segment to match, here ~ is the meaning of matching.

In addition, awk can match multiple times, as shown below:

# awk-F':'/ root/ {print $1 test.txtroot 0operator 11test 3} / test/ {print $1 camera 3} 'test.txtroot 0operator 11test 1006

In this case, the awk matches the root, then the test, and prints only the matched segments.

3. Conditional operator

Sometimes, qualifying conditions are given when matching characters, such as 0 in paragraph 3. The example commands are as follows:

# awk-F':'$3 million = "0" / etc/passwdroot:x:0:0:root:/root:/bin/bash

In awk, we can use logical symbols to judge, for example, = = equals, or it can be understood as an exact match. In addition, there are >, > =,

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