Static functions in C

A static function in C is a function that has a scope that is limited to its object file. This means that the static function is only visible in its object file. A function can be declared as static function by placing the static keyword before the function name.

An example that demonstrates this is given as follows −

There are two files first_file.c and second_file.c. The contents of these files are given as follows −

Contents of first_file.c

static void staticFunc(void)
{
   printf("Inside the static function staticFunc() ");
}

Contents of second_file.c

int main()
{
   staticFunc();
   return 0;
}

Now, if the above code is compiled then an error is obtained i.e “undefined reference to staticFunc()”. This happens as the function staticFunc() is a static function and it is only visible in its object file.

A program that demonstrates static functions in C is given as follows −

Example

#include <stdio.h>

static void staticFunc(void){
   printf("Inside the static function staticFunc() ");
}

int main()
{
   staticFunc();
   return 0;
}

Output

The output of the above program is as follows −

Inside the static function staticFunc()

In the above program, the function staticFunc() is a static function that prints ”Inside the static function staticFunc()”. The main() function calls staticFunc(). This program works correctly as the static function is called only from its own object file.