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Editor to share with you how to use sed and awk in regular expressions, I believe most people do not know much about it, so share this article for your reference. I hope you will learn a lot after reading this article. Let's learn about it together.

II. Sed

The main way to use sed is to use its find and exchange functions.

Command format sed-n'/ /'p filename in single quotation marks

Create a directory and copy the passwd file in

Show only the lines we need to find-n

Specify an interval print

Implement multiple,-e

Find a file and list it regardless of case-I

Delete some lines and put the rest of the rows out d

Sed deletes the selected line-I

Globally specify to replace 1pm 10 lines s

S stands for substitution, plus g represents the global, and not adding g will only replace the first one that appears in this line.

Adjust string position-r

Adjust the position of the first and last paragraph

Add a character to the front of the document, such as aaa

III. Awk

The-F option specifies the delimiter, if no delimiter is added, with a space or tab as the delimiter

Print is a print action, $1 is the first paragraph $2 is the second paragraph $3 the third paragraph $0 represents all

Print everything

Match a character or string

Print the first line containing oo

Print multiple times or match multiple times

Conditional operator

, > =, < if you enclose a number in double parentheses when comparing with a number, it will not be considered a number

It will be thought of as a character, or a number without double parentheses.

Exact matching

List the lines whose third paragraph is greater than 500 and print

! = is not equal to, the seventh paragraph is not equal to / sbin/nologin.

You can use & & and |, denote and and, respectively, or

Awk built-in variables

OFS, similar to the-F option, also defines the split symbol, but it is defined at the time of output

NR represents the line number

NF indicates how many segments there are after being separated by a delimiter.

OFS usage:

NF usage: indicate how many segments, list the segment number

NR usage: indicate how many lines, list the line number

Awk mathematical operation

There is no cut delimiter, you can define the delimiter with OFS

Precise matching

Awk calculates the sum of a segment

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