shell命令awk使用例：

1. 通过脚本打印出系统当前内存使用的百分比：

#!/bin/bash
[centos@centos shell]$ free -m
              total        used        free      shared  buff/cache   available
Mem:           1819         508         130          11        1180        1130
Swap:          2047         368        1679
[centos@centos shell]$ vim useCache.sh
echo "此脚本可以用来cha看当前系tong 内存使用百分比"
use=$(free -m | grep Mem: | awk '{print $3}')
total=$(free -m | grep Mem: | awk '{print $2}')
useper=$(expr $use \* 100 / $total)
echo "系tong当前内存使用百分比wei : "
echo ${useper}%
[centos@centos shell]$ chmod +x useCache.sh
[centos@centos shell]$ ./useCache.sh
此脚本可以用来cha看当前系tong 内存使用百分比
系tong当前内存使用百分比wei :
27%
[centos@centos shell]$

2. 以空格为分隔，显示每行有多少字段

[centos@centos shell]$ vim file
aaaaaaaa bbbbb ccccc dddddd eeeee fffffff

bbbbbbbbbb aaaaa ccccccc ddddddddd eeeeeeeeee

ccccccc bbbbbbb eeeeee hhhhhhhhh

eeeeee ffffff

ffffff
[centos@centos shell]$ awk '{print NF}' file
6
0
5
0
4
0
3
0
2
0
1

3. 以空格为分隔，查看文件中字段数大于4的行

[centos@centos shell]$ awk 'NF>4 {print}' file
aaaaaaaa bbbbb ccccc dddddd eeeee fffffff
bbbbbbbbbb aaaaa ccccccc ddddddddd eeeeeeeeee
[centos@centos shell]$

4. 显示每一行的行号

[centos@centos shell_study]$ awk '{print NR, $0}' file
1 aaaaaaaa bbbbb ccccc dddddd eeeee fffffff
2
3 bbbbbbbbbb aaaaa ccccccc ddddddddd eeeeeeeeee
4
5 ccccccc bbbbbbb eeeeee hhhhhhhhh
6
7 fffff hhhhhhh yyyyyyyy
8
9 eeeeee ffffff
10
11 ffffff
[centos@centos shell_study]$ awk 'NR==5 {print}' file
ccccccc bbbbbbb eeeeee hhhhhhhhh

5. 不显示第一行

[centos@centos shell_study]$ route -n | awk 'NR!=1{print}'
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.150.1   0.0.0.0         UG    100    0        0 ens33
192.168.122.0   0.0.0.0         255.255.255.0   U     0      0        0 virbr0
192.168.150.0   0.0.0.0         255.255.255.0   U     100    0        0 ens33
[centos@centos shell_study]$ route -n | awk 'NR>1{print}'
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.150.1   0.0.0.0         UG    100    0        0 ens33
192.168.122.0   0.0.0.0         255.255.255.0   U     0      0        0 virbr0
192.168.150.0   0.0.0.0         255.255.255.0   U     100    0        0 ens33

6. 匹配文件中包含 root 的行

[centos@centos shell_study]$ awk -F: '/root/' /etc/passwd
root:x:0:0:root:/root:/bin/bash
operator:x:11:0:operator:/root:/sbin/nologin

7. 不匹配文件中包含 root 的行

[centos@centos shell_study]$ awk -F: '!/root/' /etc/passwd

8. 匹配文件中空行的行号

[centos@centos shell_study]$  awk '{if($0~/^$/)print NR}' file
2
4
6
8
10

9. 不匹配文件中包含 root 的行

[centos@centos shell_study]$ awk -F: '!/root/' /etc/passwd

[centos@centos shell_study]$ awk -F: '{if($3>100)print "LARGE";else print "SMALL"}' /etc/passwd