How can I copy a file from one directory to another in c/c++

Question

I am looking for a simple example on how to copy a file from one directory to another in C. The program should only use cross platform functions that are native to C.

Answer 1

Here is a simple untested C program that does what you need:

#include 
#include 
#include 
#include 

int main(int argn, char * argv[]) {

    int src_fd, dst_fd, n, err;
    unsigned char buffer[4096];
    char * src_path, dst_path;

    // Assume that the program takes two arguments the source path followed
    // by the destination path.

    if (argn != 3) {
        printf("Wrong argument count.\n");
        exit(1);
    }

    src_path = argv[1];
    dst_path = argv[2];

    src_fd = open(src_path, O_RDONLY);
    dst_fd = open(dst_path, O_CREAT | O_WRONLY);

    while (1) {
        err = read(src_fd, buffer, 4096);
        if (err == -1) {
            printf("Error reading file.\n");
            exit(1);
        }
        n = err;

        if (n == 0) break;

        err = write(dst_fd, buffer, n);
        if (err == -1) {
            printf("Error writing to file.\n");
            exit(1);
        }
    }

    close(src_fd);
    close(dst_fd);
}