C语言链表库存更新功能求助：字符串匹配与文件更新异常

现存问题及对应修复 #

1. 字符串输入匹配失败 #

• 问题根源：更新函数仅对比当前curr节点，未遍历整个链表查找匹配的物资编码；输入验证循环错误使用逗号表达式，未正确调用strcmp判断减号输入；code数组长度（10）小于结构体中supplyCode长度（20），可能导致输入截断。
• 修复措施：
  • 遍历整个链表，逐个对比节点的supplyCode与用户输入；
  • 修正输入验证条件，正确使用strcmp判断+/-；
  • 将code数组长度调整为20，与结构体定义一致。

2. 库存数量增减运算失效 #

• 问题根源：仅实现了数量增加逻辑，未处理减少情况；以追加模式打开文件，仅写入修改后的数量，未更新整个库存记录；未确保操作的是匹配到的目标节点。
• 修复措施：
  • 添加数量减少的分支逻辑；
  • 以写入模式（"w"）打开文件，重新写入整个链表的更新后数据；
  • 找到匹配节点后，针对该节点执行数量运算。

3. 字符串未以零结尾警告 #

• 问题根源：局部字符串数组未初始化，gets_s在极端情况下可能无法正确终止字符串。
• 修复措施：初始化局部字符串数组为全0；使用scanf_s时指定输入长度，确保字符串正确终止。

修改后的完整代码 #

链表结构体定义 #

struct donations
{
    char supplyName[100], supplyCode[20], donator[150];
    int no_ofShipment;
    float quantityReceived;
    struct donations* ptr;
} *start, *curr, *temp;

库存创建主函数（优化版） #

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

void details();
void update_DonationQuantity();

int main()
{
    int i;
    FILE *fp;
    start = curr = NULL;

    if (start == NULL)
    {
        for (i = 0; i < 5; i++)
        {
            curr = (struct donations *)malloc(sizeof(struct donations));
            memset(curr, 0, sizeof(struct donations));
            details();

            if (i == 0)
                start = temp = curr;
            else
            {
                temp->ptr = curr;
                temp = curr;
            }
        }
        
        temp->ptr = NULL;
        temp = start;
        printf("\n\t Inventory Created Successfully!");     
        printf("\n\t Recorded to the end of the list!");
    }

    if (fopen_s(&fp, "Donation.txt", "w") != 0)
    {
        printf("\nError opening file!");
        return 1;
    }

    curr = start;
    while (curr)
    {
        fprintf(fp, "%-30s", curr->supplyName);
        fprintf(fp, "%-30s", curr->supplyCode);
        fprintf(fp, "%-30s", curr->donator);
        fprintf(fp, "%10d", curr->no_ofShipment);
        fprintf(fp, "\t%.1f\n", curr->quantityReceived);
        curr = curr->ptr;
    }
    printf("\n\n\t File (records) has been created!");
    fclose(fp);
    
    printf("\n\n\n\tDisplay Inventory");
    temp = start;
    while (temp)
    {
        printf("\n\n\n\t Name of Supply: %-30s", temp->supplyName);
        printf("Supply Code: %-30s", temp->supplyCode);
        printf("Donator: %-30s", temp->donator);
        printf("No. of Shipment: %10d", temp->no_ofShipment);
        printf("\tQuantity Received: %.1f", temp->quantityReceived);
        temp = temp->ptr;
    }

    update_DonationQuantity();

    return 0;
}

void details()
{
    system("cls");
    printf("\tInventory Creation\t");

    printf("\n\n\tEnter Name of Supply: ");
    scanf_s("%99s", curr->supplyName, (unsigned)_countof(curr->supplyName));
    while (getchar() != '\n');

    printf("\n\tEnter Supply Code: ");
    scanf_s("%19s", curr->supplyCode, (unsigned)_countof(curr->supplyCode));
    while (getchar() != '\n');

    printf("\n\tEnter Donator: ");
    scanf_s("%149s", curr->donator, (unsigned)_countof(curr->donator));
    while (getchar() != '\n');

    printf("\n\tEnter No. of Shipment: ");
    scanf_s("%d", &curr->no_ofShipment);
    while (getchar() != '\n');

    printf("\n\tEnter Quantity Received: ");
    scanf_s("%f", &curr->quantityReceived);
    while (getchar() != '\n');
}

修复后的更新功能函数 #

void update_DonationQuantity()
{
    char code[20] = {0};
    char update[5] = {0};
    float quantity;
    FILE *fp;
    struct donations *target = NULL;

    printf("\n\tUpdate Donation Quantity\t\n");
    printf("\n\n\tSelect donation (CT/HS/FM/SM/OM): ");
    scanf_s("%19s", code, (unsigned)_countof(code));
    while (getchar() != '\n');

    target = start;
    while (target != NULL)
    {
        if (strcmp(code, target->supplyCode) == 0)
        {
            break;
        }
        target = target->ptr;
    }

    if (target == NULL)
    {
        printf("\n\tNo matching supply code found!");
        return;
    }

    printf("\n\tReceived/Distributed item (+/-): ");
    scanf_s("%4s", update, (unsigned)_countof(update));
    while (getchar() != '\n');

    while (strcmp(update, "+") != 0 && strcmp(update, "-") != 0)
    {
        printf("\n\tWrong input, Try Again");
        printf("\n\tReceived/Distributed item (+/-): ");
        scanf_s("%4s", update, (unsigned)_countof(update));
        while (getchar() != '\n');
    }

    printf("\n\t Enter amount: ");
    scanf_s("%f", &quantity);
    while (getchar() != '\n');

    if (strcmp(update, "+") == 0)
    {
        target->quantityReceived += quantity;
    }
    else
    {
        if (target->quantityReceived >= quantity)
        {
            target->quantityReceived -= quantity;
        }
        else
        {
            printf("\n\tInsufficient quantity!");
            return;
        }
    }

    if (fopen_s(&fp, "Donation.txt", "w") != 0)
    {
        printf("\nError opening file!");
        return;
    }

    curr = start;
    while (curr)
    {
        fprintf(fp, "%-30s", curr->supplyName);
        fprintf(fp, "%-30s", curr->supplyCode);
        fprintf(fp, "%-30s", curr->donator);
        fprintf(fp, "%10d", curr->no_ofShipment);
        fprintf(fp, "\t%.1f\n", curr->quantityReceived);
        curr = curr->ptr;
    }
    printf("\n\t Inventory updated successfully!");
    fclose(fp);

    printf("\n\n\n\tUpdated Inventory");
    temp = start;
    while (temp)
    {
        printf("\n\n\n\t Name of Supply: %-30s", temp->supplyName);
        printf("Supply Code: %-30s", temp->supplyCode);
        printf("Donator: %-30s", temp->donator);
        printf("No. of Shipment: %10d", temp->no_ofShipment);
        printf("\tQuantity Received: %.1f", temp->quantityReceived);
        temp = temp->ptr;
    }
}

内容的提问来源于stack exchange，提问作者Beginner