内存在运行时 [英] Memory at runtime

问题描述

我有说我必须在指针数组从文件中读取一个未知的文本行，并在运行时分配内存的一个问题。

I have a problem which says I have to read an unknown number of text lines from a file in an array of pointers and allocate memory at runtime.

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

int main()
{
    FILE *fp = fopen("file.txt","r");
    char *arrp[10];
    int i=1;

    while(!feof(fp))
    {
        arrp[i]=malloc(sizeof(char)*51);
        fgets(arrp[i],51,fp);
        i++;
    }

    return 0;
}

我写了这个程序，但我不知道该怎么做不先初始化数组（* ARRP [10]）。

I wrote this program but I don't know how to do it without initializing the array first (*arrp[10]).

推荐答案

我建议先计算行数。

int tmp;
int linecount = 0;
FILE *fp = fopen("file.txt","r");

while ((tmp=fgetc(fp))!=EOF) {
    if (tmp=='\n') 
         ++linecount;
}

rewind(fp); // resets the stream to beginning of file

从那里，你可以MALLOC（而不是初始化一个固定的数字）指针数组适量。

From there, you can malloc the appropriate amount of array pointers (instead of initializing a fixed number).

 char** lines;
 lines = malloc(linecount * sizeof(char*));

和使用与fgets正常，以便然后读每一行入行[I]

and use fgets as normal to then read each line into lines[i]

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