c - 在C中读取文件中的名称

Question

我有这样一个文件:

name1 nickname1
name2 nickname2
name3 nickname3

我希望我的程序读取该文件并显示姓名/昵称对。

这是我做的:

users_file = fopen("users", "r");

  while(!feof(users_file))
  {
    fscanf(users_file, "%s %s", &user.username, &user.name);
    printf("%s | %s\n", user.username, user.nickname);
  }

这是输出:

 name1 | nickname1 
 name2 | nickname2      
 name3 | nickname3 
 name3 | nickname3

为什么最后一个重复了？谢谢

Answer 1

您需要在 fscanf() 之后立即检查 feof()，或者检查 fscanf() 的返回值本身。重复最后一个是因为 fscanf() 由于达到 eof 而没有将任何新数据读入 user.username 和 user.nickname。

可能的修复:

/*
 * You could check that two strings were read by fscanf() but this
 * would not detect the following:
 *
 *    name1 nickname1
 *    name2 nickname2
 *    name3 nickname3
 *    name4
 *    name5
 *
 * The fscanf() would read "name4" and "name5" into
 * 'user.username' and 'user.name' repectively.
 *
 * EOF is, typically, the value -1 so this will stop
 * correctly at end-of-file.
 */
while(2 == fscanf(users_file, "%s %s", &user.username, &user.name))
{
    printf("%s | %s\n", user.username, user.nickname);
}

或:

/*
 * This would detect EOF correctly and stop at the
 * first line that did not contain two separate strings.
 */
enum { LINESIZE = 1024 };
char line[LINESIZE];
while (fgets(line, LINESIZE, users_file) &&
       2 == sscanf(line, "%s %s", &user.username, &user.name))
{
    printf("%s | %s\n", user.username, user.name);
}