Question

I am working in C, and have some variables that I don’t want to be global, but I do want to have get and set methods for them that can be accessed “Globaly” outside of the file. I am used to doing this in Java, but C is very different in this manner. Basically I am looking for something that follows this pseudo Code, but I have not been able to find anywhere with examples that I might look at.

main.c
#include data.h
set(b);

datalog.c
#include data.h
get(b);

data.c
private int c;
set(b){
    c = b;
}
get(c){
    return c;
}

Answer 1

You make the variable static. When a global variable is made static, its scope is restricted to the current file.

An example is as follows:

Filename: main.c

#include <stdio.h>

#include "header.h"

extern int get();
extern void set(int);

int main()
{
    set(10);
    printf("value = %d \n", get());   
    set(20);
    printf("value = %d \n", get());   
    set(30);
    printf("value = %d \n", get());   
    set(40);
    printf("value = %d \n", get());   
    return 0;
}

Filename: header.h

#include <stdio.h>

int get(void);
void set(int);

Filename: header.c

#include "header.h"

static int value = 0;

int get(void)
{
    return value;
}

void set(int new_value)
{
    value = new_value;
}

Output:

$ gcc -Wall -o main main.c header.h header.c 
$ ./main 
value = 10 
value = 20 
value = 30 
value = 40 
$