user/cat.c

1#include "kernel/types.h"2#include "kernel/fcntl.h"3#include "user/user.h"45char buf[512];67void8cat(int fd)9{10  int n;1112  while((n = read(fd, buf, sizeof(buf))) > 0) {13    if (write(1, buf, n) != n) {14      fprintf(2, "cat: write error\n");15      exit(1);16    }17  }18  if(n < 0){19    fprintf(2, "cat: read error\n");20    exit(1);21  }22}2324int25main(int argc, char *argv[])26{27  int fd, i;2829  if(argc <= 1){30    cat(0);31    exit(0);32  }3334  for(i = 1; i < argc; i++){35    if((fd = open(argv[i], O_RDONLY)) < 0){36      fprintf(2, "cat: cannot open %s\n", argv[i]);37      exit(1);38    }39    cat(fd);40    close(fd);41  }42  exit(0);43}44