Question

示例文本文件：

234765 PETER 
867574 SMITH

我试图从文本文件中获取id和string并将其保存到结构中。 id保存正常，但字符串不是。

typedef struct student 
{
    int id[DATA_SIZE];
    char *student[DATA_SIZE];
}studentinfo;
studentinfo list;

struct student *create_space(int size)
{
    struct student *tmp = (struct student*)malloc(size*sizeof(struct student));
    return(tmp);
}
struct student * readData(struct student*pointer,studentinfo v)
{
    int count =0;
    int tmpid;
    char str[256];
    FILE* in_file; 
    in_file = fopen("studentlist.txt","r");
    while(fscanf(in_file,"%d",&tmpid)!= EOF && count<DATA_SIZE)
    {
        fscanf(in_file,"%s",v.student[count]);
        //printf("%s\n",str );
        v.id[count]=tmpid;
        count++;
    }
    pointer =&v;
    return pointer;

}
int main()
{
    struct student *data;
    struct student *sdata;
    data = create_space(1);
    sdata = readData(data,list);
    //printf("%s\n",sdata->student[2] );

}

Answer 1

他们有几个问题：

fscanf()读取格式化输入，并返回读取的项目的数字。

这一行：

while(fscanf(in_file,"%d",&tmpid)!= EOF && count<DATA_SIZE)

可能是这样的：

while (count < DATA_SIZE && fscanf(in_file, "%d %255s", &list.id[count], str) == 2) {

验证每行成功读取2个值。

您没有检查in_file是否返回NULL。这样做是安全的。 malloc()的情况也是如此。

您需要为char *students[DATA_SIZE]正确创建空间，因为这是一个char *指针数组。通过malloc()或strdup()为此分配空间后，您可以将内容复制到students。

以下是执行此类操作的示例：

while (count < DATA_SIZE && fscanf(in_file, "%d %255s", &list.id[count], str) == 2) {

    /* allocate space for one student */
    list.student[count] = malloc(strlen(str)+1);
    if (!list.student[count]) {
        printf("Cannot allocate string\n");
        exit(EXIT_FAILURE);
    }

    /* copy it into array */
    strcpy(list.student[count], str);
    count++;
}

以下是一个可用于帮助您实现所需结果的示例：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define DATA_SIZE 256

typedef struct {
    int id[DATA_SIZE];
    char *student[DATA_SIZE];
} studentinfo_t;

int main(void) {
    FILE *in_file;
    studentinfo_t list;
    char str[DATA_SIZE];
    size_t count = 0;

    in_file = fopen("studentlist.txt", "r");
    if (!in_file) {
        fprintf(stderr, "%s\n", "Error reading file");
        exit(EXIT_FAILURE);
    }

    while (count < DATA_SIZE && fscanf(in_file, "%d %255s", &list.id[count], str) == 2) {
        list.student[count] = malloc(strlen(str)+1);
        if (!list.student[count]) {
            printf("Cannot allocate string\n");
            exit(EXIT_FAILURE);
        }
        strcpy(list.student[count], str);
        count++;
    }

    for (size_t i = 0; i < count; i++) {
        printf("%d %s\n", list.id[i], list.student[i]);
    }

    return 0;
}

使用fscanf（C）将字符串从文本文件保存到结构

1 个答案: