使用与fgets用C动态大小的输入 [英] Input of dynamic size using fgets in C

问题描述

我想有一个字符串（可以包含空格）作为输入。我想这样做动态分配。
我的程序的结构有点像这样。

I want to have a string(can contain spaces) as input. I want to do dynamic allocation. Structure of my program is somewhat like this.

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
typedef struct msgclient
{
    int msglen;
    int msgtype;
    char *cp;
}M1;

int main()
{
    M1 *m;
    m=malloc(sizeof(M1));
    m->msglen=5;
    m->msgtype=6;
    printf("Enter\t");
    fgets(m->cp,50,stdin);  //here
    // m->cp[strlen(m->cp)]='\0';

    printf("\n%d\n%d\n",m->msglen,m->msgtype);
    fputs(m->cp,stdout);
    return 0;
}

我想知道如何获得输入。是否有任何方式与fgets的第二个参数是动态的？

I want to know how to get input. Is there any way that the second argument of fgets be dynamic?

推荐答案

使用的函数getline（3）的-instead 与fgets（3） - 它读取一个动态分配的行

Use getline(3) -instead of fgets(3)- which reads a dynamically allocated line.

typedef struct msgclient {
  ssize_t msglen;
  int msgtype;
  char *cp;
}M1;

然后在主函数

M1 *m;
m=malloc(sizeof(M1));
if (!m) { perror("malloc"); exit(EXIT_FAILURE); };
m->msglen=0;
m->msgtype=6;
m->cp = NULL;
printf("Enter\t");
fflush(stdout);
size_t msgsize = 0;
m->msglen = getline(&msg->cp, &msgsize, stdin);

您可以考虑添加缓冲（即 msgsize ）的分配大小为结构msgclient 的附加字段

you might consider adding the allocated size of the buffer (i.e. msgsize) as an additional field of struct msgclient

注意，您或许可以考虑使用 GNU的readline 。它提供了编辑和完成设施（从终端读取时）。

Notice that you might perhaps consider using GNU readline. It offers edition and completion facilities (when reading from a terminal).

这篇关于使用与fgets用C动态大小的输入的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！