fscanf函数无法在c中读取

Question

I tried to read some data from file and insert it to queue, Insert function works well, and i tried to catch the error with printfs. I saw that in while() line there is error. The data in file forms like that

12345 2

11232 4

22311 4

22231 2

void read_file(struct Queue *head){
FILE *fp;
int natid;
int cond;
fp=fopen("patients.txt","r");

    while (fscanf(fp,"%d %d", natid, cond) != EOF)
        insert(head,natid,cond);

fclose(fp);}

Answer 1

while (fscanf(fp,"%d %d", natid, cond) != EOF)

should be

while (fscanf(fp,"%d %d", &natid, &cond) == 2)

You need to pass the address of natid and cond instead of its value as the %d s in fscanf expects an int* , not an int . And I've used == 2 so that the loop breaks in case of EOF or invalid data(like characters). Otherwise, if the file contains invalid data, the loop will turn into an infinite loop as %d will fail to scan an integer.

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You should also check if fopen was successful. fopen returns NULL in failure.

Answer 2

您必须将指针传递到fscanf()将存储值的位置，并检查所有预期的转换是否成功：

while (fscanf(fp, "%d %d", &natid, &cond) == 2)