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
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.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);
}
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。