Shell passing parameters

We can pass parameters to the script when executing the Shell script. The format of the parameters obtained in the script is: $n . n  represents a number, 1 is the first parameter to execute the script, 2 is the second parameter to execute the script, and so on...

example

In the following example, we pass three parameters to the script and output them separately, where  $0  is the filename to be executed:

#!/bin/bash # author:Rookie Tutorial # url:www.runoob.com



echo "Shell passing parameter instance!" ; 
echo "Executed file name: $0" ; 
echo "The first parameter is: $1" ; 
echo "The second parameter is: $2" ; 
echo "The third parameter is: $3 " ;

Set executable permissions for the script and execute the script. The output is as follows:

$ chmod +x test.sh 
$ ./test .sh 1 2 3 Shell pass parameter instance ! Executed
 file name: ./test.sh The first parameter is: 1 The second parameter is: 2 The third parameter is: 3

In addition, there are several special characters used to process parameters:

parameter handling illustrate
$# The number of arguments passed to the script
$* Displays all parameters passed to the script as a single string.
For example, when "$*" is enclosed in """, all parameters are output in the form of "$1 $2 ... $n".
$$ The current process ID number of the script running
$! ID number of the last process running in the background
$@ Same as $*, but used with quotes, returning each argument in quotes.
For example, when "$@" is enclosed in """, all parameters are output in the form of "$1" "$2" … "$n".
$- Displays the current options used by the shell, which has the same function as the set command .
$? Displays the exit status of the last command. 0 means no error, any other value means there is an error. 
#!/bin/bash # author:Rookie Tutorial # url:www.runoob.com



echo "Shell 传递参数实例！";
echo "第一个参数为：$1";

echo "参数个数为：$#";
echo "传递的参数作为一个字符串显示：$*";

执行脚本，输出结果如下所示：

$ chmod +x test.sh 
$ ./test.sh 1 2 3
Shell 传递参数实例！
第一个参数为：1
参数个数为：3
传递的参数作为一个字符串显示：1 2 3

$* 与 $@ 区别：

  • 相同点：都是引用所有参数。
  • 不同点：只有在双引号中体现出来。假设在脚本运行时写了三个参数 1、2、3，，则 " * " 等价于 "1 2 3"（传递了一个参数），而 "@" 等价于 "1" "2" "3"（传递了三个参数）。
#!/bin/bash
# author:菜鸟教程
# url:www.runoob.com

echo "-- \$* 演示 ---"
for i in "$*"; do
    echo $i
done

echo "-- \$@ 演示 ---"
for i in "$@"; do
    echo $i
done

执行脚本，输出结果如下所示：

$ chmod +x test.sh 
$ ./test.sh 1 2 3
-- $* 演示 ---
1 2 3
-- $@ 演示 ---
1
2
3