案例1：取出文件中的特定内容

1 [01:55:12 root@localhost ~]#who
2 root     pts/0        2021-03-10 00:02 (192.168.253.233)

 1 [01:55:28 root@localhost ~]# cat /etc/passwd
 2 root:x:0:0:root:/root:/bin/bash
 3 bin:x:1:1:bin:/bin:/sbin/nologin
 4 daemon:x:2:2:daemon:/sbin:/sbin/nologin
 5 adm:x:3:4:adm:/var/adm:/sbin/nologin
 6 lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
 7 sync:x:5:0:sync:/sbin:/bin/sync
 8 shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
 9 halt:x:7:0:halt:/sbin:/sbin/halt
10 mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
11 operator:x:11:0:operator:/root:/sbin/nologin
12 games:x:12:100:games:/usr/games:/sbin/nologin
13 ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
14 nobody:x:99:99:Nobody:/:/sbin/nologin
15 systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
16 dbus:x:81:81:System message bus:/:/sbin/nologin
17 polkitd:x:999:998:User for polkitd:/:/sbin/nologin
18 sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
19 postfix:x:89:89::/var/spool/postfix:/sbin/nologin

  

[01:56:17 root@localhost ~]# cat /etc/passwd|head -n 5|cut -d : -f 1,3-5
root:0:0:root
bin:1:1:bin
daemon:2:2:daemon
adm:3:4:adm
lp:4:7:lp

  

案例2：取出使用硬盘空间的数据 

 1 [01:29:54 root@CentOS8 ~]#df
 2 Filesystem     1K-blocks    Used Available Use% Mounted on
 3 devtmpfs         1880616       0   1880616   0% /dev
 4 tmpfs            1898924       0   1898924   0% /dev/shm
 5 tmpfs            1898924    9088   1889836   1% /run
 6 tmpfs            1898924       0   1898924   0% /sys/fs/cgroup
 7 /dev/sda3      104806400 2481444 102324956   3% /
 8 /dev/sda2        1038336  170496    867840  17% /boot
 9 /dev/sda1       52415968    7296  52408672   1% /boot/efi
10 tmpfs             379784       0    379784   0% /run/user/0

 

 1 [01:29:59 root@CentOS8 ~]#df|cut -c44-46
 2 Use
 3   0
 4   0
 5   1
 6   0
 7   3
 8  17
 9   1
10   0

  

 1 [01:30:04 root@CentOS8 ~]#df |tr -s ""
 2 Filesystem     1K-blocks    Used Available Use% Mounted on
 3 devtmpfs         1880616       0   1880616   0% /dev
 4 tmpfs            1898924       0   1898924   0% /dev/shm
 5 tmpfs            1898924    9088   1889836   1% /run
 6 tmpfs            1898924       0   1898924   0% /sys/fs/cgroup
 7 /dev/sda3      104806400 2481444 102324956   3% /
 8 /dev/sda2        1038336  170496    867840  17% /boot
 9 /dev/sda1       52415968    7296  52408672   1% /boot/efi
10 tmpfs             379784       0    379784   0% /run/user/0

  

 1 [01:46:26 root@CentOS8 ~]#df |tr -s " "|cut -d" " -f5
 2 Use%
 3 0%
 4 0%
 5 1%
 6 0%
 7 3%
 8 17%
 9 1%
10 0%

  

 1 [01:50:03 root@CentOS8 ~]#df |tr -s " "|cut -d" " -f5|tr -d %
 2 Use
 3 0
 4 0
 5 1
 6 0
 7 3
 8 17
 9 1
10 0