====== Return Values ======

<code C>
/* sum.c */
#include <stdio.h>
#include <stdlib.h>
void printhelp(char progname[]);

int main(int argc, char *argv[])
{
    int i;
    int sum = 0;

    /* Simple sanity check */
    if (argc == 1)
    {
        printhelp(argv[0]);
        return 1;
    }

    for (i=1; i<argc; i++)
    {
        sum = sum + atoi(argv[i]);
    }
    printf("Total sum: %i\n", sum);
    return 0;
}

void printhelp(char progname[])
{
    printf("%s integer ...\n", progname);
    printf("This program takes any number of "
        "integer values and sums them up\n");
}
</code>

  $ make sum
  cc     sum.c   -o sum

  $ ./sum
  ./sum integer ...
  This program takes any number of integer values and sums them up

  $ echo $?
  1

  $ ./sum 45 55 12
  Total sum: 112

  $ echo $?
  0

  
  * atoi() converts a string into an integer.
  * atol() converts a string into a long integer.
  * atoll() converts a string into a long long integer.
  * atof() converts a string into a floating-point number (of type double)