shell中特殊变量

 

1. $#    传递到脚本的参数个数
2. $$    脚本运行的当前进程PID
3. $!　 最后一个运行的后台进程PID
4. $-     当前Shell选项

5. #!/bin/sh
   
   echo "Num of arguments: $#"
   echo "Current PID: $$"
   echo "The last deforegroud PID: $!"
   echo "The current shell options: $-"
   echo "Current PID: $$"                    

   

    

    

6. #!/bin/sh
   
   echo "Num of arguments: $#"
   echo "Current PID: $$"
   sleep 10 &
   echo "The last deforegroud PID: $!"
   echo "The current shell options: $-"
   echo "Current PID: $$"