寫完（2）在完成寫入文件後編寫一堆垃圾字符

Question

我在完成寫入文件後正在編寫一堆垃圾字符，這當然不是我想要的。我的文件完成讀取後如何終止？

#include <cstdlib> 
#include <string.h> 
#include <unistd.h> 
#include <fcntl.h> 
#include <sys/types.h> 
#include <sys/stat.h> 
#include <iostream> 

using std::cerr; 
using std::endl; 

const int BUFF_SIZE = 4096; 

int main (int argc, char* argv[]) { 
    if (argc < 2) { 
     cerr << "Usage:\t./cat FILE ..." << endl; 
     return EXIT_FAILURE; 
    } // if 

    for (int i = 1; i < argc; ++i) { 
     int fd; 
     if ((fd = open(argv[i], O_RDONLY)) == -1) { 
      perror(argv[i]); 
      return EXIT_FAILURE; 
     } // if 

     char buf [BUFF_SIZE]; 
     int r; 

     while ((r = read(fd, buf, BUFF_SIZE-1)) > 0) { 
      buf[BUFF_SIZE-1] = '\0'; 
      if ((write(STDOUT_FILENO, buf, BUFF_SIZE)) == -1) { // the offending line 
       perror(argv[i]); 
       return EXIT_FAILURE; 
      } // if 
     } // while 

     if (r < 0) { 
      perror(argv[i]); 
      return EXIT_FAILURE; 
     } // if 

     if (close(fd) == -1) { 
      perror(argv[i]); 
      return EXIT_FAILURE; 
     } // if 
    } // for 
} // main 

Answer 1

很簡單。你忽略了閱讀返回的計數。你應該擺脫無意義的空終止。

while ((r = read(fd, buf, BUFF_SIZE)) > 0) { 
    if ((write(STDOUT_FILENO, buf, r)) == -1) { // the fixed line 
     perror(argv[i]); 
     return EXIT_FAILURE; 
    } // if 
} // while