Parse command line options using getopt() ..

[Humble]

I have seen lots of programs where the command line options are parsed differently and have seen that lots of logic/effort behind those programs which is not much needed.. 🙂 .. That said, the function getopt() ( also getopt_long()) can simplify the command line option parsing in a massive amount . So, use it for your programs.

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>

int print_usage( )
{

	fprintf(stderr, " \n Usage :./<program name> -i <input file> -o <output file> [vh?] \n" );
	exit(1);

}
int main (int argc, char *argv[])
{

	int option;
	int i,verbose=0;
	char *inputfile = NULL;
 	char *outputfile = NULL;

	if ( argc < 5)
	{
		print_usage();
	}
	else
	{
		while ( (option = getopt(argc, argv, "i:o:hv")) != -1)
		{

			switch (option){

			case 'i':
				inputfile = optarg;
				break;
			case 'o':
				outputfile = optarg;
				break;
			case 'v':
				verbose = 1;
				printf ("Verbose enabled:\n");
				break;
			case 'h':
			case '?':
				print_usage();
				return 1;
				
			default:
				print_usage();
			}
		}
	}
	if (optind < argc)
		printf( "Non-option arguments \n");
	for (i = optind; i <argc; i++)
	{
		printf ("%s\n", argv[i]);
	}

	return 0;
}
[root@node]$




Above is a very simplified version of the getopt() example program which accepts command line switches "-i" and "-o" with argument values.. 

[Explain above program && getopt parameters]

If we execute above program using different command line switches we could see these outputs:

[ root@node]$ ./parse_arg -i asd.txt -o hu.txt -v
Verbose enabled:
[ root@node]$ ./parse_arg -i asd.txt -o hu.txt asd
Non-option arguments 
asd
[ root@node]$ ./parse_arg -i asd.txt -o hu.txt 
[root@node]$ ./parse_arg -i asd.txt -o hu.txt -h
 
 Usage :./<program name> -i <input file> -o <output file> [vh?] 
[ root@node]$ ./parse_arg -i asd.txt -o hu.txt -v
Verbose enabled:
[root@node]$ ./parse_arg -i asd.txt -k hu.txt -v
./parse_arg: invalid option -- 'k'
 
 Usage :./<program name> -i <input file> -o <output file> [vh?] 

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