gnu readline: How to keep a history list of entered command lines

When I was assigned a project to create a text console based simulator, I am looking into how to keep a history list of entered command lines like Bash Shell. Users are allow to search through the history list by hitting UP and DOWN arrow key.

GNU readline library provides this feature, and it is pretty easy to use. Lets look at the example below:

// simple_rl.cpp
#include <stdio.h>
#include <stdlib.h>

#include <readline/readline.h>
#include <readline/history.h>

int main()
{
    char *buf;

    rl_bind_key('\t',rl_abort);//disable auto-complete

    while((buf = readline("\n >> "))!=NULL)
    {
        if (strcmp(buf,"quit")==0)
            break;

        printf("[%s]\n",buf);

        if (buf[0]!=0)
            add_history(buf);
    }

    free(buf);

    return 0;
}

I use rl_bind_key() to disable the tab key for file auto-complete that enabled by default. I will write another post for custom auto-complete using libreadline soon. add_history() is used to add the enterd inputs into the history list, and key bindings to arrow keys are enabled by default.

Compile it with g++ now:

g++ -o simple_rl{,.cpp} -lreadline

That is it, simple and nice :)

7 thoughts on “gnu readline: How to keep a history list of entered command lines

  1. Pingback: GNU readline: Implement Custom Auto-complete :: c/c++ linux programming by examples

  2. Pingback: alldevnet.com

  3. thx for the post. But I think you should add a second free(buf); at the end of the loop to avoid memory leaks, as readline will not always reuse the allocated memory space.

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