捕获来自在C命令行可变长度的字符串 [英] Capturing a variable length string from the command-line in C

问题描述

我到处找一个回答我的问题，但我还没有找到一个坚实的回答我的问题。

I've looked everywhere for an answer to my question, but I have yet to find a solid answer to my problem.

我目前在用C写程序，专门针对UNIX命令行的过程中（我使用Linux作为我的开发环境，但我想这个计划，以尽可能便携式）。现在，我有一个提示用户输入一个基本的shell。然后用户将在一个命令输入，并且该命令将被相应地进行处理。这里是code，我到目前为止有：

I'm currently in the process of writing a program in C, specifically targeting the UNIX command line (I'm using Linux as my development environment, but I'd like for this program to be as portable as possible). Right now, I have a basic shell that prompts for user input. The user will then enter in a command, and that command will be processed accordingly. Here is the code that I have so far:

/* Main.c */
int main(int argc, char **argv)
{
    while (TRUE)
    {
        display_prompt();
        get_command();
    }

    return 0;
}

/* Main.h */
void get_command()
{
    /*
     * Reads in a command from the user, outputting the correct response
     */

    int buffer_size = 20;   
    char *command = (char*) malloc(sizeof(char) * buffer_size);

    if (command == NULL)
    {
       return_error("Error allocating memory");
    }

    fgets(command, buffer_size, stdin);
    if (command[strlen(command) - 1] == '\n')
    {
        puts("It's inside the buffer.");
    }
    else
    {
        puts("It's not inside the buffer.");
    }

    free(command);
}

我最初的想法是要检查 \\ n 字符，看看它是否适合在 BUFFER_SIZE ，和如果没有的realloc（）数据扩大分配的内存。

My initial thought was to check for the \n character and see if it fit within the buffer_size, and if it didn't realloc() the data to expand the allocated memory.

然而，当我的realloc（）我的字符串，我将如何去从标准输入将剩余的数据到命令？

However, after I realloc() my string, how would I go about adding the remaining data from stdin into command?

推荐答案

使用函数getline（3）如果你真的需要。这是POSIX.1-2008。而且要知道，长度不限行是DOS攻击（OOM）一个简单的攻击向量。所以考虑一个合理的线路长度的限制，并使用与fgets（3）。

Use getline(3) if you really need. It's POSIX.1-2008. And be aware that unlimited length lines are an easy attack vector for DOS-attacks (OOM). So consider making up a reasonable line length limit, and using fgets(3).

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