#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
#include <string.h>
int main(int argc, char **argv) {
int o;
int w = 10;
while ((o = getopt(argc, argv, "w")) != -1) {
switch (o) {
case 'w' :
w = atoi(optarg);
break;
}
}
printf("%d\n", w);
}
Basically, I want -w to have if nothing is inputted.
Consider these use cases
$ gcc -Wall fileabove.c
$ ./a.out
10
$ ./a.out -w
10
$ ./a.out -w14
14
I can't get the second one to work. Is there any way I can play around with getopt to get the expected result?
Assuming you're using GNU getopt, the following should work:
while ((o = getopt(argc, argv, "w::")) != -1) {
switch (o) {
case 'w' :
if (optarg) {
w = atoi(optarg);
}
break;
A following : marks the option as requiring an argument. A double : makes the argument optional (this is a GNU extension). If there is no argument, optarg is NULL.
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