Shell脚本常用变量之$$、$0、$?、$#等

编写脚本：

[root@mysql-node1 ~]# cat vartest.sh
#!/bin/sh

bingo() {
  echo "Bingo! Below is the output of a defined function."
  echo "filelname: $0"
  echo "argument List: $@"
  echo "1st argument: $1"

  echo '############## Loop of $@ ############'
  for gee in $@
  do
    echo $gee
  done
}

echo "PID: $$"
echo `ps -ef | grep $0`
echo "filelname: $0"
echo " "

echo "returnValue of Last Shell Cmd: $?"
echo "argument List: $*"
echo "argument List: $@"
echo "number of arguments: $#"
echo "1st argument: $1"
echo "2nd argument: $2"

echo " "
bingo Apple Amazon HBO Netflix

[root@mysql-node1 ~]#

测试：

[root@mysql-node1 ~]# ./vartest.sh Arthur Morgan Freeman
PID: 1742
root 1742 1469 0 04:33 pts/0 00:00:00 /bin/sh ./vartest.sh Arthur Morgan Freeman root 1743 1742 0 04:33 pts/0 00:00:00 /bin/sh ./vartest.sh Arthur Morgan Freeman root 1745 1743 0 04:33 pts/0 00:00:00 grep ./vartest.sh
filelname: ./vartest.sh

returnValue of Last Shell Cmd: 0
argument List: Arthur Morgan Freeman
argument List: Arthur Morgan Freeman
number of arguments: 3
1st argument: Arthur
2nd argument: Morgan

Bingo! Below is the output of a defined function.
filelname: ./vartest.sh
argument List: Apple Amazon HBO Netflix
1st argument: Apple
############## Loop of $@ ############
Apple
Amazon
HBO
Netflix
[root@mysql-node1 ~]#

总结：

• $$：当前shell脚本运行时的PID；
• $0：当前运行shell脚本的文件名；
• $?：上一次运行shell命令的返回值，0表示正常；
• $#：当前运行shell脚本传入的参数个数；
• $*：当前运行shell脚本传入的参数列表；
• $@：当前运行shell脚本传入的参数列表；
• $1：当前运行shell脚本传入的第一个参数；
• $2 ：当前运行shell脚本传入的第二个参数，以此类推。