How to avoid Passing config variable in every func

Question

How can I avoid passing a "config" variable in every function which uses this configuration. what is the most accurate way to make such a behavior.

This is my code: main.c

/* Complex Numbers Linking to proper variable */
typedef struct tagConfigNames {
    char name;
    complex *cnum;
} config_names;

/* Set command to function */
struct {
    char *name;
    void (*func)(config_names[]);
} cmd[] = {{"read_comp", read_comp}, {"print_comp", print_comp}, {"halt", halt},{"not_valid", NULL} };

int main()
{
    complex a,b,c,d,e,f;
    config_names cnumbers []= {{'a', &a}, {'b', &b}, {'c', &c}, {'d', &d}, {'e', &e}, {'f', &f},
                {'A', &a}, {'B', &b}, {'C', &c}, {'D', &d}, {'E', &e}, {'F', &f},
                {'#', NULL}};
    char command[30];
    int i;

    /* Run Forever */
    while(1) 
    {
        if (scanf("%s", command) == 1) {
            for (i = 0; cmd[i].func != NULL; ++i) {
                if (strcmp(command, cmd[i].name) == 0) 
                    break;
            }

            if (cmd[i].func == NULL) {
                printf("Error: no such command!\n");
            } else {
                (*(cmd[i].func))(cnumbers);
            }
        }
    }

    return 0;
}

complex.c

complex* find_complex_number(config_names cnames[], char ch)
{
    int i;
    for (i = 0; cnames[i].cnum != NULL; i++) {
        if (cnames[i].name == ch)
            break;
    }

    return cnames[i].cnum;
}

void read_comp(complex_names cnames[]) 
{
    //....

    if ((complex_num = find_complex_number(cnames, ch)) == NULL) {
        printf("Error: No such complex number\n");
        return;
    }
    //....
}

What I am actully trying to avoid is the config_names cnumbers which is passed in every function. is there a smarter way to approach such a behavior?

EDIT:

I need to declare the complex a,b,c,d,e,f; only on the main.c file. thats why i'm avoiding global variables

Answer 1

If the "configuration" is constant for each thread of the application you might consider defining it globally.

Answer 2

If the config is constant for every thread, or you're not using threads, you may use a global variable. Otherwise you can use Thread Local Storage, it will be like a global variable but specific to each thread.

Answer 3

To expand on the above, you might want to gather all functions depending on this in a file, and make the global (or thread local) variable static there, so as keeping polution to a minimum.