Pass arguments into C program from command line

Question

So I'm in Linux and I want to have a program accept arguments when you execute it from the command line.

For example,

./myprogram 42 -b -s

So then the program would store that number 42 as an int and execute certain parts of code depending on what arguments it gets like -b or -s.

Answer 1

You could use getopt.

 #include <ctype.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 
 int
 main (int argc, char **argv)
 {
   int bflag = 0;
   int sflag = 0;
   int index;
   int c;
 
   opterr = 0;
 
   while ((c = getopt (argc, argv, "bs")) != -1)
     switch (c)
       {
       case 'b':
         bflag = 1;
         break;
       case 's':
         sflag = 1;
         break;
       case '?':
         if (isprint (optopt))
           fprintf (stderr, "Unknown option `-%c'.\n", optopt);
         else
           fprintf (stderr,
                    "Unknown option character `\\x%x'.\n",
                    optopt);
         return 1;
       default:
         abort ();
       }
 
   printf ("bflag = %d, sflag = %d\n", bflag, sflag);
 
   for (index = optind; index < argc; index++)
     printf ("Non-option argument %s\n", argv[index]);
   return 0;
 }