Question

Hi I am writing a simple client-server program. In this program I have to use getopt() to get the port number and ip address like this:

server -i 127.0.0.1 -p 10001

I do not know how can I get values from optarg, to use later in the program.

Answer 1

How about like this:

char buf[BUFSIZE+1];
snprintf(buf,BUFSIZE,"%s",optarg);

Or in a more complete example:

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

#define BUFSIZE 16

int main( int argc, char **argv )
{
    char c;
    char port[BUFSIZE+1];
    char addr[BUFSIZE+1];

    while(( c = getopt( argc, argv, "i:p:" )) != -1 )
        switch ( c )
        {
            case 'i':
                snprintf( addr, BUFSIZE, "%s", optarg );
                break;
            case 'p':
                snprintf( port, BUFSIZE, "%s", optarg );
                break;
            case '?':
                fprintf( stderr, "Unrecognized option!\n" );
                break;
        }

    return 0;
}

For more information see the documentation of Getopt.