Usage_Display

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

#define OPTARGS "dkMrRsvC:"
const char *cmdname = "heartbeat";

void
usage(void)
{    
    const char *    optionargs = OPTARGS;    //#define OPTARGS        "dkMrRsvC:"
    const char *    thislet;                //

    fprintf(stderr, "\nUsage: %s [-", cmdname);
    for (thislet=optionargs; *thislet; ++thislet) {
        if (thislet[0] != ':' &&  thislet[1] != ':') {
            fputc(*thislet, stderr);                    //output one by one
        }
    }
    fputc(']', stderr);
    for (thislet=optionargs; *thislet; ++thislet) {
        if (thislet[1] == ':') {
            const char *    desc = "unknown-flag-argument";

            /* Put a switch statement here eventually... */
            switch(thislet[0]) {
            case 'C':    desc = "Current-resource-state";
                    break;
            }

            fprintf(stderr, " [-%c %s]", *thislet, desc);
        }
    }
    fprintf(stderr, "\n");
    fprintf(stderr, "\t-C only valid with -R\n");
    fprintf(stderr, "\t-r is mutually exclusive with -R\n");
    exit(1);
}

int main(int argc, char ** argv){

    usage();

}
=====================================================================================================================
console: gcc usage -o xxx
console:

Usage: heartbeat [-dkMrRsv] [-C Current-resource-state]
    -C only valid with -R
    -r is mutually exclusive with -R