Zan Pokerznik Zan Pokerznik - 1 month ago 8
C Question

Optarg string compare C

I am a newbie in C programming, I have some experiences about C++, but nothing with C. I have a question about getopt optarg argument, which is string. I want to check if input argument of -x flag is equal to "dog". My current code looks like:

int main(int argc, char** argv){
int c;
extern char *optarg;
extern int optind;
extern int optopt;
int sum=0;
while ( (c = getopt(argc, argv, ":x:h")) != -1) {
switch (c) {
case 'h': getHelp();
break;
case 'x': if(strcmp("dog", optarg)== 0){
sum = 1;
} else {
sum = 0;
}
break;
}
}


Summarized, I want to check whether input variable for -x flag is dog or not (if so, the variable sum changes to 0). In my case the sum variable is always 0, even though input is ' ./main -x dog'.
Thank you all in advance!

Answer

Comment was not allowing me to indent the output. So here it is an answer. I tried the code in the question and I see the correct output.

[tmp]$./a.out -x cat
Sum = 0
[tmp]$./a.out -x dog
Sum = 1

Here is the code:

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

int main(int argc, char** argv){
  int c;
  extern char *optarg;
  extern int optind;
  extern int optopt;
  int sum=0;
  while ( (c = getopt(argc, argv, ":x:h")) != -1) {
      switch (c) {
          case 'h':
                break;
          case 'x':
                if(strcmp("dog", optarg)== 0){
                    sum = 1;
                } else {
                    sum = 0;
                }
                break;
        }
    }

    printf("Sum = %d\n", sum);
}