CS456 - Systems Programming

Displaying exercises/e1/solution/cp.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>

#define	K	1024

void usage(void)
{
  printf("Usage: cp <src> <dst>\n");
  exit(0);
}
void help(void)
{
  printf("Usage: cp <src> <dst>\n");
  printf("Options:\n");
  printf(" --help	Prints this help\n");
  exit(0);
}


int main(int argc, char *argv[])
{
  if (argc < 2) usage();
  if (argc == 2 && strcmp(argv[1], "--help") == 0) help();
  if (argc < 3) usage();

  int src = open(argv[1], O_RDONLY);
  if (src < 0) {
    perror("source open");
    exit(1);
  }
  int dst = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, 0666);
  if (dst < 0) {
    perror("destination open");
    exit(1);
  }

  int r;
  char buf[K];

  while ((r = read(src, buf, K)) > 0) {
    if (write(dst, buf, r) < 0) {
      perror("write");
      exit(1);
    }
  }
  if (r == -1) {
    perror("read");
    exit(1);
  }
  close(src);
  close(dst);
}