A short C program to determine if one or more network interfaces exist on FreeBSD

dexter_if_exists.c

# compile with `cc -o if_exists dexter_if_exists.c`

#include <stdio.h>
#include <sysexits.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <net/if.h>

int
main(int argc, char *argv[]) {
    int i;
    if (argc == 1) {
        fprintf(stderr, "usage: %s [ifname ...]\n", argv[0]);
        fprintf(stderr, "returns 0 if all ifname exist\n");
        return EX_USAGE;
    } else {
        for (i=1; i<argc; i++)
            if (if_nametoindex(argv[i]) == 0) return 1;
        return EX_OK;
    }
}