预备知识

多个命令称为过滤器（filter）。使用管道（pipe）连接每个过滤器。

cmd1 | cmd2 | cmd3

实战演练

• 组合两个命令

[root@shaofeng ~]# ls | cat -n > out.txt
[root@shaofeng ~]# cat out.txt
     1  1.txt
     2  backup
     3  debug.sh
     4  fname_test.sh
     5  function.sh
     6  IsRoot.sh
     7  out.txt
     8  printf.sh
     9  script.sh
    10  sleep.sh
    11  time_take.sh

• 两种方式执行过滤器：$()或者``

[root@shaofeng ~]# ./ser.sh
1 1.txt 2 backup 3 debug.sh 4 fname_test.sh 5 function.sh 6 IsRoot.sh 7 out.txt 8 printf.sh 9 script.sh 10 ser.sh 11 sleep.sh 12 time_take.sh
1 1.txt 2 backup 3 debug.sh 4 fname_test.sh 5 function.sh 6 IsRoot.sh 7 out.txt 8 printf.sh 9 script.sh 10 ser.sh 11 sleep.sh 12 time_take.sh
[root@shaofeng ~]# cat ser.sh
#!/bin/bash

cmd_output=$(ls | cat -n)
echo $cmd_output

cmd_output=`ls | cat -n`
echo $cmd_output