Command-line parsing: How to parse a string as an argument - c

Question

I am attempting to parse a command line argument, which in turn will execute an associated case within a switch statement. When I parse an integer argument (as seen in the code below), the associated case executes correctly. When I attempt to parse a string such as "CPU", I do not get the correct output.
Functioning code (parsing an integer e.g. an argument of 4 gives athe correct output of hello):
#include <stdio.h>
int main(int argc, char *argv[]) {
char execution_mode = atoi (argv[1]);
switch (execution_mode)
{
case (4) :
printf("Hello");
getchar();
break;
case (8) :
printf("Goodbye");
getchar();
break;
default:
printf("Error! execution mode is not correct");
getchar();
break;
}
return 0;
}
My attempt at parsing a string e.g. the argumentCPU:
#include <stdio.h>
int main(int argc, char *argv[]) {
typedef enum MODE { CPU, OPENMP } MODE;
MODE execution_mode = (char)argv[1];
switch (execution_mode)
{
case (CPU) :
printf("Hello");
getchar();
break;
case (OPENMP) :
printf("Goodbye");
getchar();
break;
default:
printf("Error! execution mode is not correct");
getchar();
break;
}
return 0;
}

Answer 1

You cannot convert a string to an enumerate like this. What you're doing is just converting the pointer to the string to char. Which fails.
One alternative (besides comparing first argument with strcmp) to avoid this would be to give a character value to your enumerates:
typedef enum { CPU='C', OPENMP='O' } MODE;
and now you can pick the first letter of the first argument and convert it:
MODE execution_mode = (MODE)argv[1][0];
The letters must be of course all different. And check argc>1 to see if argv[1] is valid, of course
If you want full string match, you have no other choice than using strcmp:
const char *execution_mode = argv[1];
if (strcmp(execution_mode,"CPU")==0)
{
// do something
}
else if (strcmp(execution_mode,"OPENMP")==0)
{
// do something else
}

Answer 2

With the help of the users who have answered this question, I have found a working solution by using strcmp as seen below. I have also added some error checking to ensure enough arguments have been enterred on the command-line.
#include <stdio.h>
int main(int argc, char *argv[]) {
//Ensure there are enough arguments
if (argc < 2)
{
printf("Error: not enough arguments");
exit(1);
}
typedef enum MODE { CPU, OPENMP, CUDA, ALL } MODE;
MODE execution_mode = (MODE)argv[1];
//Compare string with command-line arguments
if (strcmp("CPU", execution_mode) == 0)
{
//selects CPU case
execution_mode = CPU;
}
else if (strcmp("OPENMP", execution_mode) == 0)
{
//selects OPENMP case
execution_mode = OPENMP;
}
else
{
printf("invalid arg");
}
//Switch statement
switch (execution_mode)
{
case (CPU) :
printf("CPU MODE SELECTED");
getchar();
break;
case (OPENMP) :
printf("OPENMP MODE SELECTED");
getchar();
break;
default:
printf("Error: execution mode is not correct");
getchar();
break;
}
return 0;
}