C:打印链接列表时出现段错误

Question

我是 C 的新手，但我想构建一个程序，允许用户存储从 traceroute/tracert 获得的 IP 地址，该地址首先存储到文本文件中。然后它允许他们打印下一个/上一个跃点。我使用了链表，但打印时出现段错误。

我试着浏览了一下，但我找不到任何错误，有人会指出我的错误并指导我吗？提前致谢!!

(抱歉缩进不好!!)

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

int id = 0;
int list = 0;
int nodes = 0;

FILE *readFile(char *fileName)
{
  FILE *rawdata = fopen(fileName, "r");
  return rawdata;
}

void printMenu()
{
  printf(" ========== MENU =============\n\n");
  printf("1. Report ID of Previous Hops of a network node\n");
  printf("2. Identify the next hops of a network node\n");
  printf("3. Quit\n");
}

int getInput()
{
  int choice;
  printf("Please select your choice (1 to 3) =>: ");
  scanf("%d", &choice);
  return choice;
}

struct NodeInfo {
  int ID;
  int IP1;
  int IP2;
  int IP3;
  int IP4;
  struct NodeInfo *next;
  struct NodeInfo *prev;
};

typedef struct NodeInfo Node;
Node *Topology;

Node *createNode(int ip1, int ip2, int ip3, int ip4)
{
  Node *newNode = malloc(sizeof(Node));
  newNode->IP1 = ip1;
  newNode->IP2 = ip2;
  newNode->IP3 = ip3;
  newNode->IP4 = ip4;
  newNode->next = 0;            // NULL Pointer
  newNode->prev = 0;            // NULL Pointer
  return newNode;
}

void addToBack(Node * tempnode)
{
  Node *n = Topology;
  Node *tail = 0;
  while (n != NULL) {
    tail = n;
    n = n->next;
  }
  tail->next = tempnode;
  tempnode->prev = tail;
}


void printFile(FILE * newFile)
{

  char data[256], nth1[50], nth2[50], nth3[50], nth4[50], nth5[50],
      nth6[50], nth7[50], ip[50], ip2[15], ip2new[14];
  int linecount = -1, strlength;
  int ip1, ip2x, ip3, ip4;
  int ip11, ip21, ip31, ip41;

  if (newFile == NULL) {
    printf("There is an error with opening this file\n");
  } else {
    while (fgets(data, 256, newFile) != NULL) {

      if (linecount != 3) {
        linecount++;
        continue;
      } else {

        if (linecount == 3 && data[2] != '\0') {
          sscanf(data, "%s %s %s %s %s %s %s %s", nth1, nth2, nth3, nth4,
                 nth5, nth6, nth7, ip);
          sscanf(data, "%s %s %s %s %s %s %s %d.%d.%d.%d", nth1, nth2,
                 nth3, nth4, nth5, nth6, nth7, &ip1, &ip2x, &ip3, &ip4);

          if ((ip[0] <= 'z' && ip[0] >= 'a')
              || (ip[0] <= 'Z' && ip[0] >= 'A')) {
            sscanf(data, "%s %s %s %s %s %s %s %s %s",
                   nth1, nth2, nth3, nth4, nth5, nth6, nth7, ip, ip2);
            //Rescanning for anomaly results with additional hostname
            strncpy(ip2new, ip2 + 1, strlen(ip2) - 2);
            ip2new[strlen(ip2) - 2] = '\0';

            int i;
            char *temp;
            char *ipcmp[4];
            i = 0;
            temp = strtok(ip2new, ".");
            while (temp != NULL) {
              ipcmp[i++] = temp;
              temp = strtok(NULL, ".");
            }
            Node *tempnode = createNode(ip2new);
            if (Topology != 0) {
              addToBack(tempnode);
            } else {
              Topology = tempnode;
            }
          } else {
            printf("%s\n", ip);
            printf("%d.%d.%d.%d\n", ip1, ip2x, ip3, ip4);
            Node *tempnode2 = createNode(ip);
            if (Topology != 0) {
              addToBack(tempnode2);
            } else {
              Topology = tempnode2;
            }
            continue;
          }
        }
        if (linecount == 3 && data[2] == '\0') {
          linecount = -2;
          printf("\n");
        }
      }
    }
  }
}

void printNodes()
{
  Node *n = Topology;
  while (n != 0) {
    printf("The node is %d.%d.%d.%d\n", n->IP1, n->IP2, n->IP3, n->IP4);
    n = n->next;                // Jump to next node
  }
}

int main(int argc, char *argv[])
{

  int option, fail;
  FILE *filedata;
  char *file;
  file = argv[1];
  filedata = readFile(file);    //open file
  printFile(filedata);          //prints the ip addresses
  do {
    printMenu();
    option = getInput();
    switch (option) {
    case 1:
      printf("You have selected 1\n\n");
      fail = 0;
      printNodes();
      break;
    case 2:
      printf("You have selected 2\n\n");
      fail = 0;
      break;
    case 3:
      fail = 1;
      break;
    default:
      printf("Please enter a valid choice (1-3) \n");
      fail = 0;
      break;
    }
  } while (fail != 1);
  while (Topology != 0) {
    free(Topology);
    Topology = Topology->next;
  }
}

Answer 1

您的创建节点方法有 4 个参数:

Node *createNode(int ip1, int ip2, int ip3, int ip4)

但是您只通过传递一个参数来调用此方法:

Node *tempnode = createNode(ip2new);
Node *tempnode2 = createNode(ip);

当您的方法只接受整数时，您也会传递数组。

您的代码中至少有两个错误来源。