GNU readline

GNU readline
Basic data
Maintainer	Chet Ramey
developer	Brian Fox, Chet Ramey
Current  version	8.0 ( January 7, 2019 )
operating system	cross-platform
programming language	C.
License	GNU General Public License
The GNU Readline Library

GNU readline is a program library created and maintained by the GNU project with functions for editing lines. It is under the GPL and is used in projects such as bash . From version 6.1, readline also supports Unicode characters.

For example, supports readline a program that moved the pressure on Strg+ bthe cursor one character, Strg+ fmoves the cursor forward one character, Strg+ rscans the command buffer. These standard keyboard shortcuts are from one of the first GNU projects, the Emacs text editor . Readline supports a variety of simple functions, such as a so-called "kill ring" (a more flexible variant of a clipboard ) and command line completion . Since it is a cross-platform library, readline users allow the same line processing behavior on different operating systems.

Readline can be adapted using a configuration file that applies to the user ( ~/.inputrc) or can be program-specific. In this file it is possible to define your own key combinations and to change various other settings.

Example in C

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <readline/readline.h>
#include <readline/history.h>

int main()
{
    char* input, shell_prompt[100];

    for(;;) {
        // Configure readline to auto-complete paths when the tab key is hit.
        rl_bind_key('\t', rl_complete);

        // Create prompt string from user name and current working directory.
        snprintf(shell_prompt, sizeof(shell_prompt), "%s:%s $ ", getenv("USER"), getcwd(NULL, 1024));

        // Display prompt and read input (n.b. input must be freed after use)...
        input = readline(shell_prompt);

        // Check for EOF.
        if (!input)
            break;

        // Add input to history.
        add_history(input);

        // Do stuff...

        // Free input.
        free(input);
    }
}

Web links

• GNU readline homepage
• The Tecla command-line editing library - readline replacement with an MIT license
• Editline Library (libedit) - readline replacement with a BSD license
• rlwrap - tools that add readline functionality to running programs

Individual evidence

1. ^ In: Free Software Directory .
2. ↑ Chet Ramey: Readline-8.0 release available . January 7, 2019 (accessed June 18, 2020).