Mandatory parameter getopt in C - c

Question

I have this piece of code in C
while((i = getopt(argc, argv, ":p:h:s:n:l:f:SLNF")) != -1)
switch(i){
case 'p': printf("Porta obbligatoria\n");
break;
case 'h': printf("hostname\n");
break;
case 's': printf("Surname\n");
break;
case 'n': printf("Name\n");
break;
case 'l': printf("Login\n");
break;
case 'f': printf("Faculty\n");
break;
case 'S': printf("Print Surname\n");
break;
case 'L': printf("Print Login\n");
break;
case 'N': printf("Print First name\n");
break;
case 'F': printf("Print Faculty\n");
break;
case '?': printf("USAGE\n");
break;
default: printf("USAGE default\n");
break;
}
return 0;
}
How can I have only one mandatory parameter? In my case is p.
For example:
./MyProgram -p 80 -h 127.0.0.1
Result ok.
./MyProgram -h 127.0.0.1
Error because missing -p
Only -p.
Thanks in advance.

Answer 1

Usually you use the while loop to store the values and then check the mandatory options after the loop:
int p = -1;
while((i = getopt(argc, argv, ":p:h:s:n:l:f:SLNF")) != -1)
switch(i){
case 'p': p = (int)atol(optarg);
break;
<skipped a few options >
default: printf("USAGE default\n");
break;
}
// Check mandatory parameters:
if (p == -1) {
printf("-p is mandatory!\n");
exit 1;
}
return 0;
}