读取随机文本行的分段错误？

Question

我已经阅读了很多关于这个主题的文档，但我仍然有一些问题，我知道指针是什么，但是当我尝试使用时我遇到了一些问题，在下面的代码中，txt 文件每个只包含一个单词行。我尝试从文本中读取随机行并返回到主函数，因为我需要这个）。我在主函数中打印它，请你帮我在这段代码中更改哪个部分？（当我尝试运行此错误消息是分段错误（核心转储））

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

char word(char *file, char str[], int i);

int main() {
  char buf[512];

  char j = word("words.txt", buf, 512);
  puts(j); // print random num
}

char word(char *file, char str[], int i) {
  int end, loop, line;

  FILE *fd = fopen(file, "r");
  if (fd == NULL) {
    printf("Failed to open file\n");
    return -1;
  }

  srand(time(NULL));
  line = rand() % 100 + 1; // take random num

  for (end = loop = 0; loop < line; ++loop) {
    if (0 == fgets(str, sizeof(str), fd)) { // assign text within a random line to STR
      end = 1;
      break;
    }
  }
  if (!end)
    return (char*)str; // return the str pointer
  fclose(fd);
}

Answer 1

您重新打开了文件，可能是这种情况。如果文件在 if(!end) 部分返回 fd 未关闭，则您不会关闭该文件。 该函数需要 char 但实际上需要 char *

char word(char *file, char str, int i);

int main() {
  char * buf = malloc(sizeof(char)*512);
  char *words = "words.txt";
  char* j = word(words, buf, 512);
  puts(j); // print random num
}

char word(char *file, char str[], int i) { // FIX HERE
  int end, loop, line;

  FILE *fd = fopen(file, "r"); // 
  if (fd == NULL) {
    printf("Failed to open file\n");
    return -1;
  }

  srand(time(NULL));
  line = rand() % 100 + 1; // take random num

  for (end = loop = 0; loop < line; ++loop) {
    if (0 == fgets(str, sizeof(str), fd)) { // MAIN PROBLEM, PUT A CHAR* TO STR. 
      end = 1;
      break;
    }
  }
fclose(fd); // YOU DIDN'T CLOSE IF IT RETURNED BEFORE
  if (!end)
    return str; // return the str pointer

//NOTHING IS RETURNED HERE
return str;
// I guess the problem is here, you return nothing and the function finishes, and you try to write that nothing with puts function which may cause a seg fault.
}```