从文件读取日期到链表-解网

问：

void readDataFromFile(President **h) {
    FILE *fp = fopen("President.txt", "r");
    if (fp == NULL) {
        printf("Cannot open a file!\n");
        return;
    }

    char buffer[MAX];
    int rno, start_date, end_date;
    char name[MAX];

    while(fgets(buffer, MAX, fp) != NULL) {
        // Reading data from line
        if (sscanf(buffer, "%d %[^\n] %d-%d", &rno, name, &start_date, &end_date) != 4) {
            printf("Error trying to read file!\n");
            fclose(fp);
            return;
        }

        // Creating of new node
        President *newNode = (President*)malloc(sizeof(President));
        if (newNode == NULL) {
            printf("Memory error!\n");
            fclose(fp);
            return;
        }
        newNode->rno = rno;
        strcpy(newNode->name, name);
        newNode->start_date = start_date;
        newNode->end_date = end_date;
        newNode->next = NULL;

        // Adding new node to list
        if (*h == NULL) {
            *h = newNode;
        } else {
            President* current = *h;
            while (current->next != NULL) {
                current = current->next;
            }
            current->next = newNode;
        }
    }

    fclose(fp);
    printf("Data is added to list!\n");
}

你好。我正在尝试从文件读取到链表，但我总是收到 if（sscanf）的错误原因。我的代码有什么问题？我已经检查了几次文件中的文本，但没关系，但无论如何都无法阅读。我能得到一些帮助或一些有用的链接吗？如果您显示我可以在哪里阅读它，我准备自己管理它。

以下是输入文件中的三行示例行

1 President 2000-2004 
2 President 1932-1957 
3 President 2012-2016

C 链表扫描 fgets

给定输入行的格式，无法在发布的单个调用中解析它们。您应该使用和找到第一个和最后一个空格字符，然后用于转换数字并复制中间部分，即名称，其中可能嵌入了多个空格，例如：、。sscanfstrchr()strrchr()sscanf()strcpyTheodore RooseveltWilliam H. Taft

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

void readDataFromFile(President **h) {
    FILE *fp = fopen("President.txt", "r");
    if (fp == NULL) {
        fprintf(stderr, "Cannot open file %s: %s\n",
                "President.txt", strerror(errno));
        return;
    }

    char buffer[MAX];
    int rno, start_date, end_date, count = 0;

    // Locating the last node if any
    while (*h != NULL) {
        h = &(*h)->next;
    }

    while (fgets(buffer, sizeof buffer, fp) != NULL) {
        char *first = strchr(buffer, ' ');
        char *last = strrchr(buffer, ' ');
        if (!first || !last
        ||  (first += strspn(first, " ")) >= last 
        ||  sscanf(buffer, "%d", &rno) != 1
        ||  sscanf(last, "%d-%d", &start_date, &end_date) != 2) {
            fprintf(stderr, "invalid format: %s\n", buffer);
            break;
        }
        while (last > buffer && last[-1] == ' ')
            last--;

        // Creating of new node
        President *newNode = calloc(sizeof(*newNode), 1);
        if (newNode == NULL) {
            fprintf(sdterr, "Memory allocation error!\n");
            break;
        }
        newNode->rno = rno;
        // copy the name: use `snprintf` to prevent buffer overflow
        snprintf(newNode->name, sizeof newNode->name,
                 "%.*s", (int)(last - first), first);
        newNode->start_date = start_date;
        newNode->end_date = end_date;
        newNode->next = NULL;

        // Appending new node to list
        *h = newNode;
        h = &(*h)->next;
        count++;
    }

    fclose(fp);
    printf("%d records added to list!\n", count);
}

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