003-shell Passing parameters

I. Overview

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

Second, examples

In the following example, we pass three parameters to the script and output them separately, where the file name is executed:

#!/bin/BashEcho "Shell Pass Argument instance! ";Echo "file name executed: $ A";Echo "The first parameter is: $";Echo "The second parameter is: $-a";Echo "The third parameter is: $ $";

Set executable permissions for the script and execute the script with the output as follows:

chmod +x test. SH  $ . /test. SH 1 2 3 Shell Pass Argument instance! The file name to execute:. /test. SH The first parameter is: 1 The second parameter is: 2 The third parameter is: 3

In addition, there are several special characters for handling parameters:

The

parameter handling	description
$#	The number of arguments passed to the script /td>
$*	Displays all parameters passed to the script in a single string. If "$*" is enclosed in "", all parameters are output in the form "$ $ $n".
$$	The current process ID number for the script to run
$!	ID number of the last process running in the background
[email protected]	is the same as $*, but is used with quotation marks and returns each parameter in quotation marks. such as "[Email protected]" "" "in the case, with" $ "" $ "... All parameters are output in the form "$n".
$-	Displays the current options that the shell uses, as is the SET command function.
$?	displays the exit status of the last command. 0 means there is no error, and any other value indicates an error.

#!/bin/bashecho"Shell pass parameter instance! "; Echo " The first parameter is: $ " ; Echo " the number of parameters is: $# " ; Echo " the passed arguments are displayed as a string: $* ";

Execute the script with the output as follows:

chmod +x test. SH  $ . /test. SH 1 2 3 Shell Pass Argument instance! The first parameter is:1 The number of arguments is:3 The parameters passed as a string display:123 

$* and [email protected] Difference:

• The same point: all parameters are referenced.
• Different points: only in double quotes. Assuming that three parameters 1, 2, 3 are written when the script is run, "*" is equivalent to "1 2 3" (one parameter is passed), and "@" is equivalent to "1" "2" "3" (three parameters are passed).

#!/bin/BashEcho "--\$* Demo---" forIinch "$*"; Do    Echo$i DoneEcho "--\[email protected] Demo---" forIinch "[email protected]"; Do    Echo$i Done

Execute the script with the output as follows:

 $ chmod  +x test. sh   $.  /test. sh  1  3 --$* Demo---1  2  3 --[email protected] Demo---1  2  3  

Note: In the arguments passed for the shell script If you include spaces, you should enclose the argument in single or double quotation marks so that the script receives the parameter as a whole .

When there are parameters, you can use the method of validating the parameters to reduce the occurrence of errors:

if "  $ "  then    Echo " contains the first parameter " Else    Echo " no first parameter included " fi

Note : brackets [] must be separated from the middle of the code

reference address: http://www.runoob.com/linux/linux-shell-passing-arguments.html

003-shell passing parameters