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

#define BUFSIZE 1 /* use this instead of BUFSIZ to see how slow direct i/o is */

void error(char *fmt, ...);

int main(int argc, char *argv[]) {
     int fd, n;
     char buf[BUFSIZ];

     if (argc == 1)
	  error("please specify at least one file");

     while (--argc > 0) {
	  ++argv;
	  if ((fd=open(*argv, O_RDONLY, 0)) == -1)
	       error("unable to open file: %s", *argv);
	  while ((n=read(fd, buf, BUFSIZ)) > 0) {
	       if (write(1, buf, n) != n)
		    error("error writing file: %s", *argv);
	  }
	  if (n < 0)
	       error("error reading file: %s", *argv);
     }

     return 0;
}

void error(char *fmt, ...) {
     va_list args;
     
     va_start(args, fmt);
     fprintf(stderr, "error: ");
     vfprintf(stderr, fmt, args);
     fprintf(stderr, "\n");
     va_end(args);
     exit(1);
}