Question

I am trying to see how getopts work. I wrote the code below but not sure what I am doing wrong. Please point me :

#include<unistd.h>
.. 
..
int main( int argc, char *argv[])
{
  int ch=0;
   while((ch=getopt(argc, argv, "ltR:")!=-1) // 0 here was by mistake. Changed to -1
    {  
      printf("%d",ch); //This prints -1 
       switch(ch)
               {
                 case 'l':
                 printf("l");
                 break;
                 case 't':
                 printf("t");
                 break;
                 case 'R':
                 printf("R");
                 break;
                }
    }
   return 0;
 }

 $ ./a.out -ltR 
 $ -1
 $ ./a.out -l 
 $ -1

May be I am doing a really mistake or missing out on some aspect of my understanding of getopt.

Made changes but still gives the same result:(

Thanks,
Faizan

Answer 1

I think your while expression should be

while((ch=getopt(argc, argv, "ltR")!=-1)
{..}

and the option should end with ‘:’

while((ch=getopt(argc, argv, "ltR:")!=-1)
{..}

or two ‘:’ if switch is optional.