Command Line Arguments

Posted: April 1st, 2008 | Filed under: General | Tags: c, Command Line, Java, programming, Python

Recently in a couple class projects I have needed to use command line arguments, and the first time dealing with these can be a little confusing. So here is four short programs that simply output these arguments.

What I mean by this is that I need to accept a string while I am calling the program name. For example I am running my program called printString and I want it to display the text hello. So I run it like so

./printString.c hello

This would make my program print hello. Now I will show how its done. Its basically just like passing parameters to a normal function, except its a character string, and there is no limit to how many you can add, note that these examples are only for 1 parameter. A simple loop would allow you to output them all.

Also For the c and c++ example the argc variable is how many parameters you passed in. The reason I use 1(one) and not 0 is because arg[0] is the name of the file itself.

In Java

public class printString{
  public static void main (String[] args) {
    System.out.println(args[0])
  }
}

In c

nt main(int argc, char **argv)
{
strcpy(ip_addr_dot, argv[1]);
printf(" %s", ip_addr_dot);
return 0;
}

In c++

#include<iostream>
using namespace std;
int main(int argc, char **argv)
{
cout << argv[1];
return 0;
}

In Python

import sys
for arg in sys.argv:
print arg

Note the there is an indent in front of print.

All of these short programs output the word hello and then end.

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