从文件中读取行并将它们存储在数组中 [英] Reading lines from a file and storing them in an array

问题描述

我无法逐行从文件中读取文本并将每行存储到数组中.然后，我需要打印出我得到的数组.

I am having trouble reading text from a file line by line and storing each line into an array. I then need to print out the array that I get.

我不确定是否为该数组正确分配了空间.我在 read_one_line()函数中的 fgets()遇到了分段错误.

I'm not sure if I correctly allocated space for this array. And I'm getting a segmentation fault coming from the fgets() in my read_one_line() function.

我的代码:

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

char* read_one_line(FILE* fp, char* line);
char* allocate_mem(FILE* fp, char* line);

void print_lines(char** lines, int num_lines){
    int i;
    for(i = 0 ; i < num_lines; ++i){
        printf("%d. %s", i+1, lines[i]);
    }
}

void free_lines(char** lines, int num_lines){
    int i;

    for(i = 0 ; i < num_lines; ++i){
        free(lines[i]);
    }

    if(lines != NULL && num_lines > 0){
        free(lines);
    }
}

FILE* validate_input(int argc, char* argv[]){

    FILE* fp = NULL;

    if(argc < 2){
        printf("Not enough arguments entered.\nEnding program.\n");
        exit(0);
    }
    else if(argc > 2){
        printf("Too many arguments entered.\nEnding program.\n");
        exit(0);
    }

    fp = fopen(argv[1], "r");

    if(fp == NULL){
        printf("Unable to open file: %s\nEnding program.\n", argv[1]);
        exit(0);
    }
    return fp;
}

void read_lines(FILE* fp, char*** lines, int* num_lines) {
  *num_lines = 0;

  do {
    *num_lines += 1;
    *lines = malloc(*num_lines * sizeof(*lines));
    for(int i = 0; i < *num_lines; ++i) {
      *lines[i] = allocate_mem(fp, *lines[i]);
    }
    read_one_line(fp, *lines[*num_lines]);
  } while(read_one_line(fp, *lines[*num_lines]) != NULL);
}

char* read_one_line(FILE* fp, char* line) {
  fgets(line, sizeof(line), fp);
  return line;
}

char* allocate_mem(FILE* fp, char* line) {
  fseek(fp, 0, SEEK_END);
  int length = ftell(fp);
  fseek(fp, 0, SEEK_SET);
  line = malloc((length + 1) * sizeof(char));
  return line;
}

int main(int argc, char* argv[]){
    char** lines = NULL;
    int num_lines = 0;
    FILE* fp = validate_input(argc, argv);

    read_lines(fp, &lines, &num_lines);
    print_lines(lines, num_lines);
    free_lines(lines, num_lines);
    fclose(fp);

    return 0;
}

我们将不胜感激！

推荐答案

在函数 read_one_line 中， sizeof(line)不正确， line 是一个指针，您不会获得容器 line 的大小，但是指针本身的大小(可能为8个字节)，则需要传递容器的实际大小作为函数的参数，并在 fgets 中使用它.

In the function read_one_line, sizeof(line) is not right, line is a pointer, you won't get the size of the container line, but the size of the pointer itself (likely 8 bytes), you'll need to pass the actual size of the container as a parameter of the function and use that in fgets.

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