text: #include "types.h"
  #include "stat.h"
  #include "user.h"
  
  char buf[512];
  
  void
  cat(int fd)
  {
    int n;
  
    while((n = read(fd, buf, sizeof(buf))) > 0) {
      if (write(1, buf, n) != n) {
        printf(1, "cat: write error\n");
        exit(1); //Lab1
      }
    }
    if(n < 0){
      printf(1, "cat: read error\n");
      exit(1); //Lab1
    }
  }
  
  int
  main(int argc, char *argv[])
  {
    int fd, i;
  
    if(argc <= 1){
      cat(0);
      exit(0); //Lab1
    }
  
    for(i = 1; i < argc; i++){
      if((fd = open(argv[i], 0)) < 0){
        printf(1, "cat: cannot open %s\n", argv[i]);
        exit(1); //Lab1
      }
      cat(fd);
      close(fd);
    }
    exit(0); //Lab1
  }
  