Question

我正在尝试获取用户输入，将输入写入文件，然后使用数据作为结构。文件编译正常但在第一次输入后我收到此错误消息：

$ gcc student.c -o student  
$ ./student  
Student First Name:  
alex  
Student Last Name:  
Segmentation fault (core dumped)

代码：

/* student.h is to include the structure for stundent info */
#include <stdio.h>
#include <stdlib.h>

typedef struct {  
    char sID[9];
    char firstN[30];
    char lastN[30];
    }student[100];

#include "student.h"    
int main()
{
    FILE *sIf;
    int i;
    int num;
    student *sI;
    char *c;
    char *b;
    char *a;

    sIf = fopen("student.txt", "a+");
    if(!sIf)
    {
        printf("File could not be opened\n\a\a");
        getchar();
        return -1;
    }
    {
        printf("Student First Name: \n");
        scanf("%s", b);
        printf("Student Last Name: \n");
        scanf("%s", a);

        printf("Student ID Number: \n");
        scanf("%s", c);

        fprintf(sIf, "%s, %s\t%s\n", a, b, c);
    }

    fclose(sIf);
    return 0;
}

Answer 1

编码时始终使用适当的缩进，这使代码易于阅读。
您没有为char指针a, b, c分配内存。
而不是scanf()使用fgets()来接受输入字符串。

尝试使用此固定代码（我已在必要时添加了注释）。

/* student.h is to include the structure for stundent info */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
//#include "student.h"
typedef struct {
    char sID[9];
    char firstN[30];
    char lastN[30];
    }student[100];
int main()
{
    FILE *sIf;
    student *sI;//Why are you using it?
    char *ptr_pos;
    //Fix 1 Allocate space for a, b and c
    char *c=malloc(sizeof(char)*256);
    if(c==NULL)
    {
        puts("Failed to allocate memory for variable c");
        exit(1);
    }
    char *b=malloc(sizeof(char)*256);
    if(b==NULL)
    {
        puts("Failed to allocate memory for variable b");
        exit(1);
    }
    char *a=malloc(sizeof(char)*256);
    if(a==NULL)
    {
        puts("Failed to allocate memory for variable a");
        exit(1);
    }

    sIf = fopen("student.txt", "a+");
    if(!sIf)
    {
        printf("File could not be opened\n\a\a");
        return EXIT_FAILURE;
    }
    printf("Student First Name: \n");
    //Accept string using fgets, it prevents from overflow
    fgets(b,256,stdin);
    b[strlen(b)-1]='\0'; //Remove \n from the input string
    // Or you can use the following to remove `\n` from input string
    //if((ptr_pos=strchr(b, '\n')) != NULL)
    //  *ptr_pos = `\0`;


    printf("Student Last Name: \n");
    fgets(a,256,stdin);
    a[strlen(a)-1]='\0';

    printf("Student ID Number: \n");
    fgets(c,256,stdin);
    c[strlen(c)-1]='\0';

    fprintf(sIf, "%s, %s\t%s\n", a, b, c);       

    fclose(sIf);
    //Free allocated memory
    free(a);
    free(b);
    free(c);

    return EXIT_SUCCESS;
}

无法在C中找到导致分段错误（核心转储）的原因

1 个答案: