File IO

⬅️ CS50 Week 04 - Memory

File I/O

	// C does come with a pointer type FILE
	// that... 🥁 points to a file 
	FILE *file = fopen("phonebook.csv", "a");
 
	// always check for NULL
    if (file == NULL)
    {
        return 1;
    }

This is how you define a BYTE:

	typedef uint8_t BYTE;
 

🤔 How do you recognize a jpg file? The first three bytes of any .jpg files are: 0xff, 0xd8 and 0xff.

🤔 What is a bitmap? A map of bits 🥁

And, finally, this is how you copy a file, one byte at a time:

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
 
typedef uint8_t BYTE;
 
int main(int argc, char *argv[])
{
    // Ensure proper usage
    if (argc != 3)
    {
        fprintf(stderr, "Usage: copy SOURCE DESTINATION\n");
        return 1;
    }
 
    // open input file
    FILE *source = fopen(argv[1], "r");
    if (source == NULL)
    {
        printf("Could not open %s.\n", argv[1]);
        return 1;
    }
 
    // Open output file
    FILE *destination = fopen(argv[2], "w");
    if (destination == NULL)
    {
        fclose(source);
        printf("Could not create %s.\n", argv[2]);
        return 1;
    }
 
    // Copy source to destination, one BYTE at a time
    BYTE buffer;
    while (fread(&buffer, sizeof(BYTE), 1, source))
    {
        fwrite(&buffer, sizeof(BYTE), 1, destination);
    }
 
    // Close files
    fclose(source);
    fclose(destination);
    return 0;
}