读取C中文件中的名称

时间:2012-03-08 16:07:43

标签: c scanf feof

我有一个这样的文件:

name1 nickname1
name2 nickname2
name3 nickname3

我希望我的程序读取该文件并显示姓名/昵称配对。

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? 感谢

3 个答案:

答案 0 :(得分:3)

您需要在feof()之后立即检查fscanf(),或者检查fscanf()本身的返回值。最后一个重复,因为fscanf()由于达不到eof而未将任何新数据读入user.usernameuser.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);
}

答案 1 :(得分:1)

如果您将循环更改为:

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

然后它应该工作,请注意我们不检查EOF,我们让fscanf为我们检查。

答案 2 :(得分:0)

如果看到文件结束条件,则feof()函数返回true。如果您正在从文件中读取,情况可能并非如此。

有多种方法可以解决这个问题,即migtht的工作方式(基本上就是hmjd所说的):

while (fscanf(users_file, "%s %s", &user.username, &user.name) == 2) {
  ...
}

fscanf的返回值是已成功转换和分配的转化次数,因此如果您在阅读时获得EOF,则会与您期望的两次不同。