c - 如何使用 fscanf 从文件中读取并查找与用户输入匹配的记录

Question

我想读取用户输入并验证它是否与“user.txt”记录匹配，如果匹配则提示用户错误消息，但scanf读取的数据总是会变成随机的号码，这是代码。抱歉我的英语，因为我不是以英语为母语的人

                int day,month,year;
                char name[15];


                printf("Enter your name\n");
                scanf(" %[^\n]s",name);
                printf("Enter you birthday(dd/mm/yyyy)\n");
                scanf("%d%*[-/]%d%*[-/]%d",&day,&month,&year);
                printf("Enter your contact number (60-)\n");
                scanf("%d",&contactNumber);
                printf("Enter your postcode\n");
                scanf("%d",&postcode);

                char x [30];
                int y,z,w,d;
                int duplicateContactNum [15];
                int checkSentinel=0;

                filepointer=fopen("user.txt","r");
                if(filepointer==NULL){
                //Not exist,Print exception message
                printf("Exception Occur: Error writing text into the text file");

                }
                while(!feof(filepointer))
                {
                    fscanf(filepointer,"%s;%d/%d/%d;%d;%d\n",x,&y,&z,&w,&duplicateContactNum,&d);
                    if(strcmp(contactNumber,duplicateContactNum)==0)
                    {
                        checkSentinel++;
                        break;
                    }

                }
                if(checkSentinel!=0)
                {
                    rewind(filepointer);
                    printf("You have entered a duplicated entry\n");
                    fclose(filepointer);
                }
                else
                {
                    rewind(filepointer);
                    fclose(filepointer);
                    filepointer=fopen("user.txt","a");
                    fprintf(filepointer,"%s;%d/%d/%d;%d;%d\n",name,day,month,year,contactNumber,postcode);
                    fclose(filepointer);
                }

Answer 1

您在初始格式字符串中有一个错误，并且您没有测试 scanf 调用的返回值，因此所有返回错误都没有警告您。

            printf("Enter your name\n");
            if (1 != scanf(" %[^\n]",name)) {  // no s after [] format
                fprintf(stderr, "Error reading name\n");
                return 1;
            }
            printf("Enter you birthday(dd/mm/yyyy)\n");
            if (3 != scanf("%d%*[-/]%d%*[-/]%d",&day,&month,&year)) {
                ...
            }
            printf("Enter your contact number (60-)\n");
            if (1 != scanf("%d",&contactNumber)) {
                ...
            }
            printf("Enter your postcode\n");
            if (1 != scanf("%d",&postcode)) {
                ...
            }

记住:始终测试输入功能