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This article mainly introduces how to use linux's AWK to create files related to knowledge, the content is detailed and easy to understand, the operation is simple and fast, with a certain reference value, I believe that everyone after reading this article on how to use linux's AWK to create files will have a harvest, let's take a look at it.

Awk processing: each line is processed in turn, and then output, different from sed: awk reads to memory.

The default delimiter is a space or the tab key

Case 1:

BEGIN {} {} END {} filename

Line processing front line processing line post-processing file name

# awk 'BEGIN {print 1 ok 2} {print "ok"} END {print "- -"}' / etc/hosts

Or:

[root@awk ~] # cat / etc/hosts | awk 'BEGIN {print 1 + 2} {print "ok"} END {print "-"}'

0.5

Ok

Ok

-

Records and fields

Awk assumes that its input is structured rather than an irregular string of characters. By default, it takes each input line as a record and words separated by spaces or tabs as fields.

Awk is treated as a record: a line is a record, because the string separated by a newline character by default in awk is a record. (default\ nnewline character: record delimiter)

Record: a string split by a record splitter defaults to newline\ n

Field: a string split by a field separator defaults to single or multiple "" tab keys.

= =

Variables in awk:

$0: represents the entire line

NF: number of statistical fields

$NF: it is number finally, which represents the information of the last column

RS: enter record delimiter

ORS: output record delimiter.

NR: print record number, (line number)

FNR: you can separate and print line numbers according to different files.

FS: enter the field delimiter, which defaults to a space.

The field delimiter of the OFS output, default to a space.

FILENAME filename the name of the file to be processed

$1 first field, $2 second field, and so on.

Case study:

FS (input field delimiter)-generally abbreviated to-F (before line processing)

[root@awk ~] # cat / etc/passwd | awk 'BEGIN {FS= ":"} {print $1}'

Root

Bin

Daemon

Adm

Lp

Sync

Shutdown

Halt

Mail

Operator

Games

[root@awk ~] # cat / etc/passwd | awk-F:'{print $1}'

Root

Bin

Daemon

Adm

Lp

Sync

Shutdown

Halt

Mail

Operator

Note: if-F is not added by default, it is distinguished by space!

=

OFS (output field delimiter)

[root@awk ~] # cat / etc/passwd | awk 'BEGIN {FS= ":"; OFS= ".."} {print $1 drawing 2}'

Root..x

Bin..x

Daemon..x

Adm..x

Lp..x

Sync..x

Shutdown..x

Halt..x

Mail..x

=

1. Create two files

[root@awk ~] # vim a.txt

Love

Love.

Loove

Looooove

[root@awk ~] # vim file1.txt

Isuo

IPADDR=192.168.246.211

Hjahj123

GATEWAY=192.168.246.1

NETMASK=255.255.255.0

DNS=114.114.114.114

NR represents the record number, and when awk records the behavior, this variable is equivalent to the current line number

[root@awk ~] # awk'{print NR,$0} 'a.txt file1.txt

1 love

2 love.

3 loove

4 looooove

five

6 isuo

7 IPADDR=192.168.246.211

8 hjahj123

9 GATEWAY=192.168.246.1

10 NETMASK=255.255.255.0

11 DNS=114.114.114.114

FNR: represents the record number, and when awk records the behavior, this variable is equivalent to the current line number (separate files)

[root@awk ~] # awk'{print FNR,$0} 'a.txt file1.txt

1 love

2 love.

3 loove

4 looooove

five

1 isuo

2 IPADDR=192.168.246.211

3 hjahj123

4 GATEWAY=192.168.246.1

5 NETMASK=255.255.255.0

6 DNS=114.114.114.114

=

RS (enter record delimiter)

1. Create a file

[root@awk ~] # vim passwd

Root:x:0:0:root:/root:/bin/bashbin:x:1:1:bin:/bin:/sbin/nologin

[root@zabbix-server ~] # cat passwd | awk 'BEGIN {RS= "bash"} {print $0}'

Root:x:0:0:root:/root:/bin/

Bin:x:1:1:bin:/bin:/sbin/nologin

ORS (output record delimiter)

two。 Make changes to the file just now

[root@awk ~] # vim passwd

Root:x:0:0:root:/root:/bin/bash

Bin:x:1:1:bin:/bin:/sbin/nologin

Daemon:x:2:2:daemon:/sbin:/sbin/nologin

[root@awk ~] # cat passwd | awk 'BEGIN {ORS= "} {print $0}'

Root:x:0:0:root:/root:/bin/bash bin:x:1:1:bin:/bin:/sbin/nologin daemon:x:2:2:daemon:/sbin:/sbin/nologin

=

NF: number of statistical columns

[root@awk ~] # cat / etc/passwd | awk-F:'{print NF}'

seven

seven

seven

seven

$NF: print the last column

[root@awk ~] # cat / etc/passwd | awk-F:'{print $NF}'

/ bin/bash

/ sbin/nologin

/ sbin/nologin

/ sbin/nologin

/ sbin/nologin

Exercise 1: merge files into one line

[root@awk ~] # cat / etc/passwd | awk 'BEGIN {ORS= ""} {print $0}'

Exercise 2: divide a line into multiple lines

1. First create a file

[root@awk ~] # vim d.txt

Root:x:0:0:root:/root:/bin/bash

[root@awk ~] # cat d.txt | awk 'BEGIN {RS= ":"} {print $0}'

Root

X

0

0

Root

/ root

1. Print the second and third columns in a file

# cat / etc/passwd | awk-F:'{print $2 recording 5}'

two。 Prints a character of the specified column in the specified row

# free-m | awk 'NR==2 {print $2}'

3. Count the number of lines in a file

# cat / etc/passwd | awk'{print NR}'

4. Using if conditional judgment in awk

+ + I: add from 1, and assignment is in operation

ISuppli: add from 0, and the operation is assigning

If statement:

{if (expression) {statement; statement;.}}

Show administrator user name

# cat / etc/passwd | awk-F:'{if ($3 million / 0) {print $1 "is administrator"}}'

Statistical system users

# cat / etc/passwd | awk-F:'{if ($3 > = 0 & & $3)

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