The Ultimate Guide To Batch File Programming PART- 4

Parameters: Giving Information to Batch Programs

To make batch programs really intelligent you need to be able to provide them with parameters which are nothing but additional valuable information which is needed to ensure that the bath program can work efficiently and flexibly.To understand how parameters work, look at the following script:

Code:
@ECHO OFF
ECHO First Parameter is %1
ECHO Second Parameter is %2
ECHO Third Parameter is %3

The script seems to be echoing(printing) messages on the screen, but what do the strange symbols %1 , % 2 etc stand for? To find out what the strange symbols stand for save the above script and go to DOS and execute this script by passing the below parameters:

C:\windows>batch_file_name abc def ghi
This batch file produces the following result:
C:\windows>batch_file_name abc def ghi
First Parameter is abc
Second Parameter is def
Third Parameter is ghi
The first line in the output is produced by the code line:
ECHO First Parameter is %1

Basically what happens is that when DOS encounters the %1 symbol, it examines the original command used to execute the bath program and look for the first word (argument) after the batch filename and then assigns %1 the value of that word. So one can say that in the ECHO statement %1 is replaced with the value of the first argument. In the above example the first word after the batch file name is abc, therefore %1 is assigned the value of this word.

The %2 symbol too works in the similar way, the only difference being that instead of the first argument, DOS assigns it the value of the second argument, def. Now all these symbols, %1, %2 are called replaceable parameters. Actually what happens is that %1 is not assigned the value of the first argument, but in fact it is replaced by the value of the first argument.If the batch file command has more parameters than what the batch file is looking for, then the extras are ignored. For example, if while executing a batch file program , we pass four arguments, but the batch file program requires only 3 parameters, then the fourth parameter is ignored.

To understand the practical usage of parameters, let's take up a real life example. Now the following script requires the user to enter the name of the files to be deleted and the folder in which they are located.

Code:
@ECHO OFF
CD\
CD %1
DEL %2

This script can be called from the DOS prompt in the following way:

C:\windows>batch_file_name windows\temp *.tmp

In a single script we cannot use more that nine replaceable parameters. This

means that a particular batch file will have replaceable parameters from %1 to
%9.Infact there is a tenth replaceable parameter, the %0 parameter. The %0
parameter contains the name of the batch file itself.

Important: Say you want to execute a batch file and once the procedure of execution is complete, want to leave DOS and return to Windows, what do you do? The EXIT command can be used in such situations. So simply end your batch file with the EXIT command.

EXIT

ABOUT THE AUTHOR

AbhiShek SinGh
Founder of 'TheHackingArticles'. Cyber Security Analyst, Cyber Security Researcher, and Software Engineer. Follow 'AbhiShek SinGh' on Facebook , Twitter or Google+ or via Email

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