将文本文件读取到链表数组时出现分段错误

Question

read_to_list 函数旨在扫描文件的内容 - dump.txt - 并将其加载到单链表数组中。

问题出在main函数的LINE 2：read_to_list(argv[1]);

dump.txt 文件包含以下信息：

Name        Group Size
----------------------------------
Anna         2
Bill         4
Connor       6
Denise       8

argv[1] 与我在命令行上声明的一个文本文件相关，以便在运行程序后从我的链表中转储数据。退出程序后，.txt 文件以上述格式保存数据。

我不知道为什么在 CLI 中传递的文件上调用 read_to_list 函数时出现分段错误，因为在我看来该函数应该正确加载数据并且该函数是在 main 函数的正确位置调用。

感谢您为我提供的任何帮助！

代码如下：

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

typedef struct node
{
    char name[20];
    int size;
    struct node *next;
}node;

node* head[4]={NULL,NULL,NULL,NULL};
node* tail[4]={NULL,NULL,NULL,NULL};



void read_to_list(char *filename)
{
    FILE *fp;
    int mined_partysize;
    char mined_partyname[20];

    char header = "Name\t\tGroup Size\n----------------------------------\n";

    fp = fopen(filename, "r");
    if (fp == NULL)
        return;

    fseek(fp, strlen(header), SEEK_SET);
    printf("This is working1");
    while(fscanf(fp, "%s%d", mined_partyname, &mined_partysize) == 2)
    {
        printf("This is working2");
        if(mined_partysize == 0)
        {
            printf("\nThat is not a valid command. Party not added!\n");
        }
        if(mined_partysize >= 1 && mined_partysize <= 2)
        {
            add_party(0, mined_partyname, mined_partysize);
        }
        else if(mined_partysize >= 3 && mined_partysize <= 4)
        {
            add_party(1, mined_partyname, mined_partysize);
        }
        else if(mined_partysize >= 5 && mined_partysize <= 6)
        {
            add_party(2, mined_partyname, mined_partysize);
        }
        else if(mined_partysize >= 7)
        {
            add_party(3, mined_partyname, mined_partysize);
        }
    }

    fclose(fp);
    return;
}


//
// main function
//


int main(int argc, char *argv[])
{
    int x;
    read_to_list(argv[1]);
    while (1)
    {
        fflush(stdin);
        printf("\n\nEnter 1 to add a party\nEnter 2 to remove a party\nEnter 3 for the list of the party\nEnter 4 to change party size.\nEnter 5 to quit.\n\n");

        // user interface
        scanf("%d",&x);
        char name[20];
        int size;
        switch(x)
        {

            case 1:
                printf("\nParty Name: ");
                scanf("%s", name);
                printf("\nParty Size: ");
                scanf("%d", &size);
                if(size == 0)
                {
                    printf("\nThat is not a valid command. Party not added!\n");
                }
                if(size >= 1 && size <= 2)
                {
                    add_party(0, name, size);
                }
                else if(size >= 3 && size <= 4)
                {
                    add_party(1, name, size);
                }
                else if(size >= 5 && size <= 6)
                {
                    add_party(2, name, size);
                }
                else if(size >= 7)
                {
                    add_party(3, name, size);
                }
                break;

            case 2:
                printf("\nSize of party to delete: ");
                scanf("%i", &size);
                delete_party(NULL, size);
                break;

            case 3:
                list_parties();
                break;

            case 4:
                change_partysize(name, size);
                break;

            case 5:
                write_to_file(argv[1]);
                exit(0);
                break;

            default:
                continue;
        }
    }
}


//
//add function
//


void add_party(int h, char *name, int size)
{
    //declare file pointer
    FILE *fp;

    //to be used by fscanf
    int number;

    //create a new node
    int i=0;
    int breaker = 0;
    node *p;
    node *new_item;

    new_item = (node *)malloc(sizeof(node)); // allocate memory the size of the struct

    strcpy(new_item->name,name);
    new_item->size = size;

    if(head[h] == NULL && tail[h] == NULL) // if an empty list, create a head and tail
    {
        head[h] = new_item;
        tail[h] = head[h];
        new_item->next = NULL;
        return;
    }

    //traversal
    for(i=0; i<4; i++)
    {
        p = head[i];
        while(p != NULL)
        {
            //check that no repeating names. delete nodes that do have repeating names
            if(strcmp(p->name,name) == 0)
            {
                printf("\nSorry, that name is already taken\n");
                free(new_item);
                return;
            }
            p = p->next; //go to the next node in the list
        }
    }
    tail[h]->next = new_item;
    new_item->next = NULL;
    tail[h] = new_item;


}

Answer 1

您正在取消引用一个空指针。