Shell scripts from getting started to complex three (passing parameters)

when executing a Shell script, parameters can be passed to the 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, and 2 is the second parameter that executes the script ...

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

# Cat Test.sh

#!/bin/bash

echo "Shell pass parameter Example";

echo "File name: $";

echo "First parameter: $";

echo "second parameter: $";

echo "The third parameter: $ A";

Output results

# sh test.sh 1 2 3

Shell Pass-Through parameters example

File name: test.sh

First parameter: 1

Second parameter: 2

Third parameter: 3

The following special characters are used to handle parameters:

Parameter handling instructions

$# The number of arguments passed to the script

$* Displays all parameters passed to the script in a single string.

such as "$*" in the Case of "" ", in the form of" $ $ ... $n "output all parameters.

$$ The current process ID number for the script to run

$! ID Number of the last process running in the background

[Email protected] Same as $*, but quoted when used, and returns each parameter in quotation marks.

such as "[email protected]" with "" "in the case, with" $ "" $ "... All parameters are output in the form "$n".

$- shows 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.

$* 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).

The following example:

# VI test.sh

#!/bin/bash

For i in "$*";d o

Echo $i

Done

echo "------------"

For i in "[email protected]";d o

Echo $i

Done

Output

# sh test.sh 1 2 3

1 2 3

------------

1

2

3

Shell scripts from getting started to complex three (passing parameters)