PASS Parameters in Shell: [reprint]. PASS Parameters in shell.

PASS Parameters in Shell: [reprint]. PASS Parameters in shell.
PASS Parameters through Shell

When executing a Shell script, we can pass parameters to the script. The parameters obtained in the script are in the following format:$ N.NRepresents a number, 1 is the first parameter for executing the script, 2 is the second parameter for executing the script, and so on ......

Instance

In the following example, we pass three parameters to the script and output them separately.$0Is the execution File Name:

#! /Bin/bash # author: cainiao tutorial # url: www. runoob. comecho "Shell passing parameter instances! "; Echo" executed file name: $0 "; echo" first parameter: $1 "; echo" second parameter: $2 "; echo "third parameter: $3 ";

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

$ Chmod + x test. sh $./test. sh 1 2 3 Shell passing parameter instances! Name of the file to be executed:./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 Processing	Description
$ #	Number of parameters passed to the script
$ *	Display All parameters passed to the script with a single string. For example, when "$ *" is included in... $ N "to output all parameters.
$	ID of the current process that the script runs
$!	ID of the last process running in the background
$ @	It is the same as $ *, but it is enclosed in quotation marks and each parameter is returned in quotation marks. For example, when "$ @" is included in "... All parameters are output in the form of "$ n.
$-	Displays the current options used by Shell, which have the same function as the set command.
$?	Displays the exit status of the last command. 0 indicates no error, and any other value indicates an error.

#! /Bin/bash # author: cainiao tutorial # url: www. runoob. comecho "Shell passing parameter instances! "; Echo" the first parameter is: $1 "; echo" the number of parameters is: $ # "; echo" The passed parameters are displayed as a string: $ *";

Run the script and the output result is as follows:

$ Chmod + x test. sh $./test. sh 1 2 3 Shell passing parameter instances! The first parameter is: 1. The number of parameters is: 3. The passed parameter is displayed as a string: 1 2 3.

Difference between $ * and $:

• Similarities: All parameters are referenced.
• Difference: It is only reflected in double quotation marks. If three parameters 1, 2, and 3 are written during the script running, "*" is equivalent to "1 2 3" (passing a parameter ), "@" is equivalent to "1" "2" "3" (three parameters are passed ).

#! /Bin/bash # author: cainiao tutorial # url: www. runoob. comecho "-- \ $ * demo ---" for I in "$ *"; do echo $ idoneecho "-- \ $ @ demo ---" for I in "$ @"; do echo $ idone

Run the script and the output result is as follows:

$ Chmod + x test. sh $./test. sh 1 2 3 -- $ * demo --- 1 2 3 -- $ @ demo --- 123