You need to read the man page for getopt()
while ((ch = getopt(argc, argv, "dhlprtns")) != -1)
^^^^^^^^
This does not correspond to the way you are using the arguments. You want colons ":" after the flags which expect arguments. In your code "d" is not followed by a colon and yet you seem to want an value for it:
case 'd':
debug_flag=atoi(optarg); /* print address in output */
break;
So what is happening is you are calling atoi(0)
and this is seg faulting.
Here's the example from the man page, note how "b" is not followed by a colon while "f" is.
#include <unistd.h>
int bflag, ch, fd;
bflag = 0;
while ((ch = getopt(argc, argv, "bf:")) != -1) {
switch (ch) {
case 'b':
bflag = 1;
break;
case 'f':
if ((fd = open(optarg, O_RDONLY, 0)) < 0) {
(void)fprintf(stderr,
"myname: %s: %s\n", optarg, strerror(errno));
exit(1);
}
break;
case '?':
default:
usage();
}
}
argc -= optind;
argv += optind;