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Passing arguments to your program

Passing arguments to your program, How to use & impliment int argc char argv functionality

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no2pencil

13 Jul, 2007 - 09:51 AM

Post #1

int main(int argc, char *argv[])
** How to use & impliment int argc char argv functionality aka passing arguments to your program **

In order to allow your program to accept arguments, you need to declair 2 items in your main function. Those being integer argc & the charactor argv array. These two items accept the arguments, & allow you to use them inside of your program. This will both be explained in detail, as well examples will be given.

Argc is the integer value of how many arguments have been passed. It is important to remember that the default value will be the command itself. So for example, if 3 arguments are passed, then argv[1] will be the command, giving argc a value of 4 (0 through 4). If your program absolutly must recieve a specific number of arguments, you can use this value to break execution, & then prompt the user on the usage of your program.

Argv is the other value being passed, & it is a charactor array. You can use argv[] to referance each array, or argv[][] to referance each charactor of each array, or a 2d array.

Code example:

CODE

#include <stdio.h>

// main program
int main(int argc,char *argv[]) {
    int i=1;
    // decode arguments
    if(argc < 2) {
        printf("You must provide at least one argument\n");
        exit(0);
    }
    // report settings
    for (;i<argc;i++) printf("Argument %d:%s\n",i,argv[i]);
    return(0);
}

Usage examples:

CODE

server:/home/user/code>./prog
You must provide at least one argument

CODE

server:/home/user/code>./prog help me out
Argument 1:help
Argument 2:me
Argument 3:out

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Amadeus

15 Jul, 2007 - 06:21 AM

Post #2

For clarity's sake, the argv, or argument vector, parameter is actually a pointer to an array of string pointers.

Alternate:

http://publications.gbdirect.co.uk/c_book/...ts_to_main.html

tralfas

9 Mar, 2008 - 07:53 PM

Post #3

wow that was very helpful i always wondered what those were for and now i know. thanks!

Panarchy

10 May, 2009 - 04:51 AM

Post #4

Thanks for the tutorial, I was given the link to this in my most recent topic.

I was also told in my most recent topic that we shouldn't be using printf in C++, that we should instead use cout.

Can this tutorial please be rectified?

Thanks in advance,

Panarchy

no2pencil

19 May, 2009 - 11:10 PM

Post #5

QUOTE(Panarchy @ 10 May, 2009 - 06:51 AM)

I was also told in my most recent topic that we shouldn't be using printf in C++, that we should instead use cout.

Can this tutorial please be rectified?

As long as you understand the difference, use whatever output method that you prefer. Something as trivial as writing to standard output should not require a re-write of the tutorial, since the purpose of the tutorial is to convey the usage of passing arguments to your program.

As well, there is no C Tutorials to submit this to. So again, I see no reason to change such a minor detail. I hope that you can still find this tutorial useful.