Английская Википедия:GNU Readline
Шаблон:Short description Шаблон:Infobox software GNU Readline is a software library that provides in-line editing and history capabilities for interactive programs with a command-line interface, such as Bash. It is currently maintained by Chet Ramey as part of the GNU Project.
It allows users to move the text cursor, search the command history, control a kill ring (a more flexible version of a copy/paste clipboard) and use tab completion on a text terminal. As a cross-platform library, readline allows applications on various systems to exhibit identical line-editing behavior.
Editing modes
Readline supports both Emacs and vi editing modes, which determine how keyboard input is interpreted as editor commands. See Шаблон:Section link.
Emacs keyboard shortcuts
Emacs editing mode key bindings are taken from the text editor Emacs.
On some systems, Шаблон:Key press must be used instead of Шаблон:Key press, because the Шаблон:Key press shortcut conflicts with another shortcut. For example, pressing Шаблон:Key press in Xfce's terminal emulator window does not move the cursor forward one word, but activates "File" in the menu of the terminal window, unless that is disabled in the emulator's settings.
- Шаблон:Key press : Autocompletes from the cursor position.
- Шаблон:Key press : Moves the cursor to the line start (equivalent to the key Шаблон:Key press).
- Шаблон:Key press : Moves the cursor back one character (equivalent to the key Шаблон:Key press).
- Шаблон:Key press : Sends the signal SIGINT via pseudoterminal to the current task, which aborts and closes it.Шаблон:Efn
- Шаблон:Key press
- Sends an EOF marker, which (unless disabled by an option) closes the current shell (equivalent to the command
exit). (Only if there is no text on the current line) - If there is text on the current line, deletes the current character (then equivalent to the key Шаблон:Key press).
- Sends an EOF marker, which (unless disabled by an option) closes the current shell (equivalent to the command
- Шаблон:Key press : (end) moves the cursor to the line end (equivalent to the key Шаблон:Key press).
- Шаблон:Key press : Moves the cursor forward one character (equivalent to the key Шаблон:Key press).
- Шаблон:Key press : Abort the reverse search and restore the original line.
- Шаблон:Key press : Deletes the previous character (same as backspace).
- Шаблон:Key press : Equivalent to the tab key.
- Шаблон:Key press : Equivalent to the enter key.
- Шаблон:Key press : Clears the line content after the cursor and copies it into the clipboard.
- Шаблон:Key press : Clears the screen content (equivalent to the command
clear). - Шаблон:Key press : (next) recalls the next command (equivalent to the key Шаблон:Key press).
- Шаблон:Key press : Executes the found command from history, and fetch the next line relative to the current line from the history for editing.
- Шаблон:Key press : (previous) recalls the prior command (equivalent to the key Шаблон:Key press).
- Шаблон:Key press : (reverse search) recalls the last command including the specified characters. A second Шаблон:Key press recalls the next anterior command that corresponds to the search
- Шаблон:Key press : Go back to the next more recent command of the reverse search (beware to not execute it from a terminal because this command also launches its XOFF). If you changed that XOFF setting, use Шаблон:Key press to return.
- Шаблон:Key press : Transpose the previous two characters.
- Шаблон:Key press : Clears the line content before the cursor and copies it into the clipboard.
- Шаблон:Key press : If the next input is also a control sequence, type it literally (e. g. * Шаблон:Key press Шаблон:Key press types "^H", a literal backspace.)
- Шаблон:Key press : Clears the word before the cursor and copies it into the clipboard.
- Шаблон:Key press Шаблон:Key press : Edits the current line in the $EDITOR program, or vi if undefined.
- Шаблон:Key press Шаблон:Key press : Read in the contents of the inputrc file, and incorporate any bindings or variable assignments found there.
- Шаблон:Key press Шаблон:Key press : Incremental undo, separately remembered for each line.
- Шаблон:Key press Шаблон:Key press : Display version information about the current instance of Bash.
- Шаблон:Key press Шаблон:Key press : Alternates the cursor with its old position. (C-x, because x has a crossing shape).
- Шаблон:Key press : (yank) adds the clipboard content from the cursor position.
- Шаблон:Key press : Sends the signal SIGTSTP to the current task, which suspends it. To execute it in background one can enter
bg. To bring it back from background or suspensionfg ['process name or job id'](foreground) can be issued. - Шаблон:Key press : Incremental undo, separately remembered for each line.
- Шаблон:Key press : (backward) moves the cursor backward one word.
- Шаблон:Key press : Capitalizes the character under the cursor and moves to the end of the word.
- Шаблон:Key press : Cuts the word after the cursor.
- Шаблон:Key press : (forward) moves the cursor forward one word.
- Шаблон:Key press : Lowers the case of every character from the cursor's position to the end of the current word.
- Шаблон:Key press : Cancels the changes and puts back the line as it was in the history.
- Шаблон:Key press : Capitalizes every character from the cursor's position to the end of the current word.
- Шаблон:Key press : Insert the last argument to the previous command (the last word of the previous history entry).
Choice of the GPL as GNU Readline's license
GNU Readline is notable for being a free software library which is licensed under the GNU General Public License (GPL). Free software libraries are far more often licensed under the GNU Lesser General Public License (LGPL), for example, the GNU C Library, GNU gettext and FLTK. A developer of an application who chooses to link to an LGPL licensed library can use any license for the application.[1] But linking to a GPL licensed library such as Readline requires the entire combined resulting application to be licensed under the GPL when distributed, to comply with section 5 of the GPL.[2][3]
This licensing was chosen by the FSF on the hopes that it would encourage software to switch to the GPL.[4] An important example of an application changing its licensing to comply with the copyleft conditions of GNU Readline is CLISP, an implementation of Common Lisp. Originally released in 1987, it changed to the GPL license in 1992,[5] after an email exchange between one of CLISP's original authors, Bruno Haible, and Richard Stallman, in which Stallman argued[6] that the linking of readline in CLISP meant that Haible was required to re-license CLISP under the GPL if he wished to distribute the implementation of CLISP which used readline.[7]
Another response has been to not use this in some projects, making text input use the primitive Unix terminal driver for editing.
Alternative libraries
Alternative libraries have been created with other licenses so they can be used by software projects which want to implement command line editing functionality, but be released with a non-GPL license.
- Many BSD systems have a BSD-licensed libedit.[8] MariaDB and PHP allow for the user to select at build time whether to link with GNU Readline or with libedit.[9][10]
- linenoise is a tiny C library that provides line editing functions.[11]
- Haskeline is a BSD-3-Clause licensed readline-like library for Haskell. It is mainly written for the Glasgow Haskell Compiler,[12] but is available to other Haskell projects which need line-editing services as well.[13]
- PSReadLine is a BSD-2-Clause licensed readline implementation written in C# for PowerShell inspired by bash and GNU Readline[14]
Sample code
The following code is in C and must be linked against the readline library by passing a Шаблон:Mono flag to the compiler:
#include <stdlib.h>
#include <stdio.h>
#include <readline/readline.h>
#include <readline/history.h>
int main()
{
// Configure readline to auto-complete paths when the tab key is hit.
rl_bind_key('\t', rl_complete);
// Enable history
using_history();
while (1) {
// Display prompt and read input
char* input = readline("prompt> ");
// Check for EOF.
if (!input)
break;
// Add input to readline history.
add_history(input);
// Do stuff...
// Free buffer that was allocated by readline
free(input);
}
return 0;
}
Bindings
Non-C programming languages that provide language bindings for readline include
- Python's built-in Шаблон:Code module;
- Ruby's built-in Шаблон:Code module;[15]
- Perl's third-party (CPAN) Шаблон:Code module, specifically Шаблон:Code for GNU ReadLine.
Support for readline alternatives differ among these bindings.
Notes
References
External links
