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Shell passing parameters

We can in the implementation of Shell script to pass parameters to the script, the script takes parameters within theformat: $ n.n represents a number, 1 for the first execution of the script parameter, 2 for the second parameter to execute the script, and so on /en/en/en

Examples

The following examples we pass three parameters to the script, and outputs, where $ 0 is the name of the file to execute: 

#!/bin/bash
# author:本教程
# url:www.w3write.com

echo "Shell 传递参数实例！";
echo "执行的文件名：$0";
echo "第一个参数为：$1";
echo "第二个参数为：$2";
echo "第三个参数为：$3";

Set executable permissions to the script and execute the script, the output is as follows: 

$ chmod +x test.sh 
$ ./test.sh 1 2 3
Shell 传递参数实例！
执行的文件名：./test.sh
第一个参数为：1
第二个参数为：2
第三个参数为：3

In addition, there are several parameters to handle special characters:

Parameter handling Explanation
$ # The number of parameters passed to the script
$ * In a single string displays all parameters passed to the script.
Such as "$ *" with "" "enclosed case, the form of" $ 1 $ 2 /en. $ n "output of all parameters.
$$ The current process ID number of the script runs
$! Finally, a process running in the background ID number
$ @ * $ With the same, but when you use quotation marks, and returns each parameter in quotes.
Such as "$ @" with "" "enclosed case, the form of" $ 1 "" $ 2 "/en." $ n "output of all parameters.
$ - Shell displays the current option to use, and set the command the same function.
$? Displays exit status of the last command. 0 indicates no errors, and any other value indicates an error. 
#!/bin/bash
# author:本教程
# url:www.w3write.com

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

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

Execute the script, the output is as follows: 

$ 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

$ * And $ @ difference:

  • The same point: all references to all parameters.
  • Differences: only reflected in double quotes. Suppose the script runs when writing the three parameters 1,2,3 ,, "*" is equivalent to "123" (pass a parameter), and "@" is equivalent to "1", "2", " 3 "(passed three parameters). 
#!/bin/bash
# author:本教程
# url:www.w3write.com

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

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

Execute the script, the output is as follows: 

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

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Shell passing parameters
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