Separate 9 numbers of type double from command-line in c with strtok() and strtod()

Question

I have the following command-line interface with a -k parameter that looks like this: -k "0.0:-1.0:0.0:-1.0:4.0:-1.0:0.0:-1.0:0.0". These are 9 double values separated by ":". I've managed to separate the first double value 0.0 with strtok() and strtod() but I need all 9 values and I don't seem to find an efficient way to do it.

Maybe with a loop and then save the values in a 2x3 array but no results yet. In the end, I have to use these numbers to manipulate pixels in an image. Note that these are example numbers and the user can type any double value from 0 to let's say 255. Hope someone can help with some advice.

Below is the code on how I managed to separate the first value. I would appreciate any advice on how to solve this, thank you!

char *kernel_input; 
char *end = NULL;
kernel_input = strtok(kArg, ":");

if(kernel_input == 0)
{
  /* ERROR */
}

double value_1 = (double) strtod(kernel_input, &end);

Answer 1

Would you please try something like:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define ARYSIZE 100                     // mamimum number of elements

/*
 * show usage
 */
void
usage(char *cmd)
{
    fprintf(stderr, "usage: %s -k value1:value2:..\n", cmd);
}

/*
 * split str, store the values in ary, then return the number of elements
 */
int
parsearg(double *ary, char *str)
{
    char *tk;                           // each token
    char *err;                          // invalid character in str
    char delim[] = ":";                 // the delimiter
    double d;                           // double value of the token
    int n = 0;                          // counter of the elements

    tk = strtok(str, delim);            // the first call to strtok()
    while (tk != NULL) {                // loop over the tokens
        d = strtod(tk, &err);           // extract the double value
        if (*err != '\0') {             // *err should be a NUL character
            fprintf(stderr, "Illegal character: %c\n", *err);
            exit(1);
        } else if (n >= ARYSIZE) {      // #tokens exceeds the array
            fprintf(stderr, "Buffer overflow (#elements should be <= %d)\n", ARYSIZE);
            exit(1);
        } else {
            ary[n++] = d;               // store the value in the array
        }
        tk = strtok(NULL, delim);       // get the next token (if any)
    }
    return n;                           // return the number of elements
}

int
main(int argc, char *argv[])
{
    int i, n;
    double ary[ARYSIZE];

    if (argc != 3 || strcmp(argv[1], "-k") != 0) {
                                        // validate the argument list
        usage(argv[0]);
        exit(1);
    }

    n = parsearg(ary, argv[2]);         // split the string into ary

    for (i = 0; i < n; i++) {           // see the results
        printf("[%d] = %f\n", i, ary[i]);
    }
}

If you execute the compiled command e.g.:

./a.out -k "0.0:-1.0:0.0:-1.0:4.0:-1.0:0.0:-1.0:0.0"

It will output:

[0] = 0.000000
[1] = -1.000000
[2] = 0.000000
[3] = -1.000000
[4] = 4.000000
[5] = -1.000000
[6] = 0.000000
[7] = -1.000000
[8] = 0.000000

If you put an invalid charcter in the string, the program will print an error message and abort.