Question

I am new to C programming. When I include the blank.h file into the Test.c file the program will not compile, however when I include blank.c file into the Test.c file it compiles fine. Below is the source for all the .c and .h files. Im using gcc as my compiler, and I have a feeling I need to do some sort of linking with it? Any help would be great thanks!

This is the Test.c source

#include <stdio.h>
#include "blank.h"
#include "boolean.h"

int main()  
{
    bool result = blank("");

    printf("%d\n", result);

    return 0;
}

This is the blank.h source

// Header file for blank function

bool blank(char string[]);

This is the blank.c source

#include "boolean.h"
#include "blank.h"
#include <regex.h>

bool blank(char string[])
{

    regex_t regex_blank;
    int blank = regcomp(&regex_blank, "[:blank:]", 0);

    blank = regexec(&regex_blank, string, 0, NULL, 0);

    if  ( string == NULL || blank == 1 )
        return true;
    else
        return false;
}

and finally the boolean.h

// Boolean

// Define true
#ifndef true
#define true 1
#endif

// Define false
#ifndef false
#define false 0
#endif

typedef int bool;

Answer 1

Ok, so I tried the source code you provided. There were a couple problems. Here are the exact steps of how I built, what I fixed. See if this works for you:

Created 4 files in a folder: Test.c, blank.c, blank.h and boolean.h
Copied code over.

From the shell ran:

 gcc Test.c blank.c -o b

Output:

In file included from Test.c:2:0:
blank.h:3:1: error: unknown type name ‘bool’
blank.c: In function ‘blank’:
blank.c:11:46: error: ‘NULL’ undeclared (first use in this function)
blank.c:11:46: note: each undeclared identifier is reported only once for each function it appears in

To fix the first error:
In blank.h added this on top: #include "boolean.h"

To fix the second error:
In blank.c added this after the other includes: #include <stdlib.h>

Once again the terminal ran:

 gcc Test.c blank.c -o b

then from the terminal ran ./b and it prints 1.