shell脚本执行的区别

  1 #!/bin/bash
  2 
  3 . subshell-test.sh
  4 
  5 echo "test.sh"
  6 echo 
  7 echo 
  8 echo $$
  9 echo "$! = $!" 

test.sh 

  1 #!/bin/bash
  2 
  3 (echo "Subshell running...";echo " jeffrey is comming...";echo $$)
  4 
  5 echo $!
  6 echo "main..."
  7 echo $$

subshell-test.sh 

. subshell-test.sh: (注意点号后面有个空格）表示读取后面这个shell脚本中的内容在当前脚本中执行. 他不会另起子shell.

我的理解就是把subshell-test.sh中的内容copy到test.sh中执行。

因为二者PID是相同的：

jeffrey@jeffrey-Aspire-4743:~$ ./test.sh 
Subshell running...
jeffrey is comming...
<strong>5196</strong>

main...
<strong>5196</strong>
test.sh


<strong>5196</strong>
$! = 

./subshell-test.sh:是重新开启新的子shell

jeffrey@jeffrey-Aspire-4743:~$ ./test.sh 
Subshell running...
jeffrey is comming...
<strong>5214</strong>

main...
<strong>5214</strong>
test.sh


<strong>5213</strong>
$! =