cat w/ system call

gistfile1.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

static void do_cat(const int fd, const char *path);
static void die(const char *s);

int main(int argc, char const *argv[])
{

  if (argc < 2) {
    do_cat(STDIN_FILENO, "STDIN");
  } else { 
    int i;
    for (i = 1; i < argc; i++) {
      char *path = (char*) argv[i];
      do_cat(open(path, O_RDONLY), path);
    }
  }
  exit(0);


}

#define BUFFER_SIZE 2048

static void do_cat(const int fd, const char *path)
{
 
 if (fd < 0) {
   die(path);
 }

 unsigned char buf[BUFFER_SIZE];
 int n;

 for (;;) {
   n = read(fd, buf, sizeof buf);
   if (n < 0) {
     die(path);
   }
   if (n == 0) {
     break;
   }
   if (write(STDOUT_FILENO, buf, n) < 0) {
     die(path);
   }
 }

 if (close(fd) < 0) {
   die(path);
 }
  
}

static void die(const char *s)
{
  perror(s);
  exit(1);
}