C:从文件中读取未知数量的未知长度的行

Question

我正在尝试编写一个程序，该程序读取未知数量的未知长度的行(使用malloc)并将它们保存到结构中。

当我尝试打印结构中保存的内容时，出现段错误。

代码:

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

typedef struct line{
    struct line* next_line;
    char* data;
}line;

line* read_line(line* ptrLine, FILE* pFile);

int main(int argc, char *argv[])
{
    if(argc < 2){
        return 2;
    }

    FILE* pFile;

    if((pFile = fopen(argv[1], "r")) == NULL){
        return 1;
    }

    line* list_beginning = NULL;
    line* curr_line;

    curr_line = read_line(list_beginning, pFile);

    while(1){
        if(fgetc(pFile) == EOF) break;
        fseek(pFile, -1, SEEK_CUR);
        curr_line = read_line(curr_line, pFile);
    }

    //printf("%c", (list_beginning->data[0]));
    /*while(curr_line->next_line != NULL){
        unsigned int i = 0;
        for(i = 0; i < strlen(curr_line->data); i++){
            printf("%c", curr_line->data[i]);
        }
    }*/

    fclose(pFile);
    return 0;
}

line* read_line(line* ptrLine, FILE* pFile){

    ptrLine = malloc(sizeof(line));

    ptrLine->data = malloc(1024*sizeof(char));
    int curr_position = 0;
    char c;

    while(1){
        c = fgetc(pFile);
        if(c == '\n' || c == EOF) {
            *(ptrLine->data + curr_position) = '\0';
            break;
        }
        *(ptrLine->data + curr_position) = c;
        curr_position++;
    }

    ptrLine->next_line = NULL;
    return ptrLine->next_line;
}

Answer 1

line* read_line(line* ptrLine, FILE* pFile){

ptrLine = malloc(sizeof(line));

ptrLine->data = malloc(1024*sizeof(char));
int curr_position = 0;
char c;

while(1){
    c = fgetc(pFile);
    if(c == '\n' || c == EOF) {
        *(ptrLine->data + curr_position) = '\0';
        break;
    }
    *(ptrLine->data + curr_position) = c;
    curr_position++;
}

ptrLine->next_line = NULL;
return ptrLine->next_line;

}

在此代码中，最后两行不好:

  ptrLine->next_line = NULL
  return ptrLine->next_line;

您将 next_line 设置为 NULL 并返回它，以便您的“read_line”函数返回“NULL”为了避免这种情况，请将最后一行更改为:

   return ptrLine;