I'm tired of in-lining shader code and forgot how to read the contents of a file in C.

openAndReadFile.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>

int main()
{
	const char *FILENAME = "shader.glsl";
	FILE *shader;

#ifdef _WIN32
	errno_t error = fopen_s(&shader, FILENAME, "r");
	if (error == 0) {
#else
	if (vs = fopen(FILENAME, "r")) {
#endif
		struct stat st;
		long fileSize;
		if (stat(FILENAME, &st) == 0)
		{
			fileSize = st.st_size;
		}
		long charLength = sizeof(char) * fileSize;
		char *source = malloc(charLength);
		size_t retCode = fread(source, sizeof *source, charLength, shader);
		for (unsigned int i = 0; i < retCode; i++)
		{
			printf("%c", source[i]);
		}
		free(source);
		fgetc(stdin);
	}
	else
	{
		printf("Error loading file: %s", error);
		fgetc(stdin);
	}

	return 0;
}