以下代码有什么问题？我试图在文本文件中搜索记录

The program runs fine till I create the file and enter records from structure, but when I try to search a record by using roll no, it crashes.

程序运行正常，直到我创建文件并从结构中输入记录，但是当我尝试使用roll no搜索记录时，它会崩溃。

I am using a structure called student to store data and then I am creating a text file and then I use a for loop to write data on the text file. Then I reopen the file and try to search a record using student roll no.

我正在使用一个名为student的结构来存储数据然后我创建一个文本文件，然后我使用for循环在文本文件上写入数据。然后我重新打开文件并尝试使用学生卷号搜索记录。

Program runs fine until I try to search the student roll no. It crashes right after I enter the student roll no to be searched.

程序运行正常，直到我尝试搜索学生卷号。在我输入要搜索的学生卷之后它立即崩溃。

Can anyone tell me what modification is needed to make the search work?

谁能告诉我需要哪些修改才能使搜索工作？

Below is my code:

以下是我的代码：

#include<stdio.h>


 struct student {

    int roll_no;
    char name [80];
    int age;

    }st[30],s;



   int main ()

{
int i,n;
char fname[80];
int search;
int found;

FILE *fp;

printf("\nEnter the file name : \n");
scanf("%s",fname);
fp=fopen(fname,"w");
if(fp==NULL)
{
    printf("\nCannot create file :");
    exit(0);
}

printf("\nNumber of students : \n");
scanf("%d",&n);
for(i=0;i<n;i++)
{
    printf("\n\nInformation for student#%d : \n\n",i+1);

    printf("\nStudent roll number :  \n" );
    scanf("%d",&st[i].roll_no);
    printf("\nStudent name: \n: ");
    scanf("%s",st[i].name);
    printf("\nStudent age : ");
    scanf("%d", &st[i].age);

}

fprintf(fp, "\nStudent roll no\t\t Student name\t\t student age\t\t\n\n");
for(i=0;i<n;i++)
{
    fprintf(fp, "\n%d          \t\t %s           \t\t %d          \t\t", st[i].roll_no,st[i].name,st[i].age);


}
fclose(fp);

fp=fopen(fname,"r+t");
if(fp==NULL)
{
    printf("\nCannot open file\n");
    exit(0);
}
printf("\n\nStudent roll no to be searched : ");
found=0;
scanf("%d", search);


while(!(feof(fp)) && (found==0))
{
    fscanf(fp,"%d,%s,%d",&s.roll_no,s.name,&s.age);
    if(s.roll_no==search)
    {
        fseek(fp,-sizeof(struct student), SEEK_CUR);
        printf("\nEnter new name : \n");
        scanf("%s", s.name);
        fprintf(fp, "\n%d          \t\t %s           \t\t %d          \t\t", s.roll_no,s.name,s.age);

        found=1;
    }
}

if(found=0)
{
    printf("\nStudent record doesn't exist \n");
}
fclose(fp);
return 0;
}

1 个解决方案

#1

In your code, you're missing an address-of operator in scanf(), thereby passing an invalid type of argument. Basically

在你的代码中，你在scanf（）中缺少一个address-of运算符，从而传递了一个无效的参数类型。基本上

 scanf("%d", search);

should be

应该

scanf("%d", &search);

That said, it is always a good practice to size-limit the inputs for string, like, for an array defined like char fname[80];, you should use

也就是说，对于字符串的输入进行大小限制总是一个好习惯，例如，对于像char fname [80]这样定义的数组，你应该使用

scanf("%79s",fname);

to avoid possible buffer overflow by excessively long input.

通过过长的输入来避免可能的缓冲区溢出。

Also, always check for the return value of scanf() and family of functions to ensure their success.

此外，始终检查scanf（）和函数系列的返回值，以确保它们的成功。

#1