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A C++ commandline for use in servers and chat software. Provides very simple asynchronous input/output.

License: MIT License

CMake 6.75% C++ 93.25%
async cplusplus cpp cpp11 cpp17 cross-platform readline terminal

commandline's Introduction

commandline

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A cross-platfrom C++11 commandline for use in servers and terminal chat software. Provides very simple asynchronous input/output.

Callback-based i/o supported, as well as history, autocomplete, custom prompts, and more (see features)

Example

#include "commandline.h"

int main() {
    Commandline com;
    while (true) {
        if (com.has_command()) {
            auto command = com.get_command();
            com.write("got command: " + command);
        }
        std::this_thread::sleep_for(std::chrono::milliseconds(100));
        com.write("this is a message written with com.write");
    }
}

Result:

main.cpp demo gif

Features

  • Asynchronous I/O: The user can type into stdin while the program spams output onto stdout, with no visual issues. A command or message is committed with the Enter/Return key.

  • Scrolling input: If the entered line is too long to fit on screen, it gets scrolled left / right.

  • Thread-safety: All output is buffered internally and protected with mutexes, so write() can be called by many threads at the same time without issues. Performance-wise this makes little impact, in our testing, as compared to usual printf() or std::cout logging (it's much faster than the latter in common scenarios).

  • Tab Autocomplete: A callback on_autocomplete makes it possible to build your own autocomplete.

  • History: History of all commands entered is saved, if the history was enabled with Commandline::enable_history(). The history can be navigated like expected, with the up- and down-arrow keys, as well as cleared by the program, saved and restored, and more.

  • Cursor movement: Even though an internal buffer is used (and the usual buffered input is disabled), the cursor can be moved as usual with the left- and right-arrow keys, and moved to the front and back with the HOME and END keys.

  • has_command() and get_command(), or on_command callback: All these are supported as ways to get a line that was entered by the user, allowing many ways to integrate the library into existing applications.

  • Cross-platform: Works on any POSIX system with a terminal that supports ANSI (all of the ones you can find, probably), as well as WinAPI console applications and Microsoft CMD, and MacOS.

Installation

Vcpkg

For vcpkg users there is a lionkor-commandline port that can be installed via vcpkg install lionkor-commandline or by adding it to dependencies section of your vcpkg.json file.

Building from source

  1. Install cmake and a compiler of your choice (on Windows you want Visual Studio (not Visual Studio Code), on Linux either gcc, clang or some other compiler, and on MacOS clang / "apple clang").
  2. Clone this repository somewhere.
  3. Run cmake . -B bin in the cloned repository, with any options you'd like (e.g. -DCMAKE_BUILD_TYPE=Release for a release build).
  4. Run cmake --build bin --parallel to build the library and tests.

It should have then built the library, which you can link against.

You could also put add_subdirectory(commandline) to your CMakeLists, if you clone the repo in the folder such that commandline is a subfolder to your CMakeLists.txt.

Why not X?

Why not GNU readline?

Because it's GPL licensed, which makes it difficult to integrate into more permissive licensed or closed-source / commercial projects. commandline aims to be usable by anyone, as long as MIT license terms are followed.

Why not curses/ncurses?

They're TUI frameworks, this is much less than a TUI. They're also C, which is less handy for C++ projects.

How to use

  1. Construct a Commandline instance. A prompt can optionally be passed in this constructor, or via set_prompt.
Commandline com;
  1. Query for new commands in a loop - this should usually be your main server loop or something similar.
bool is_running = true;
while (is_running) {
  // check if something was entered
  if (com.has_command()) {
    // grab the command from the queue
    // note: undefined if has_command wasn't checked beforehand
    std::string command = com.get_command();
    if (command == "quit") {
      is_running = false;
    }
  }
}
  1. To write to the commandline, use Commandline::write.
com.write("hello, world!");

How to contribute?

We roughly follow issue-driven development, as of v1.0.0. This means that any change you want to make should first be formulated in an issue. Then, it can be implemented on your own fork, and the issue referenced in the commit (like fix #5). Once PR'd and merged, it will automatically close the issue.

Use the .clang-format and the clang-format tool to format your code before submitting.

How does it work?

To support reading and writing at the same time, it's using VT100 ANSI escape codes. This means that, on windows, you need to enable those for your CMD terminal.

Before a new line is output into stdout, the current input line is cleared, the output line is written, and the input line is rewritten in the line below, positioning the cursor where it was, as if nothing happened. This results in the illusion that the input line is fixed below the output, which is a very natural design.

In most terminals and in Microsoft's CMD.exe (as well as standalone WinAPI console applications), this happens instantly and no visual glitches appear, which makes it very fun and smooth to use.

Used In

Commandline is used in https://github.com/BeamMP/BeamMP-Server!

commandline's People

Contributors

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commandline's Issues

Handle implementation defined behavior on input etc

Currently, calling get_command without checking has_command invokes implementation defined behavior (i.e. in both currently present backends an exception).

  • Find all cases in the code where such assumptions are made
  • Check and handle such errors
  • Come up with a uniform and clean way to handle such errors

Set cursor position from on_autocomplete callback

on_autocomplete currently passes in the current cursor position, in order to allow autocomplete within a word/sentence at a specific point. This is nice, but not as useful as it could be, because the cursor will end up at the end of the autocompletion, which is the end of the entire input.

We need a way to set the cursor's position generally, like c.set_cursor_position(), but it also has to be understood by the caller of on_autocomplete whether or not this has been called. If it was called, dont put the cursor at the end, and if it wasn't, do.

Use WinAPI functions on Windows

Currently we're using ANSI escape codes on both Unix/Linux/MacOS and Windows, which causes issues in Windows (of course).

They decided that Powershell and the Windows Terminal (!= CMD) should not behave properly when presented with ANSI escape codes, even with that feature explicitly enabled.

So, instead of getting really angry with windows' decisions, we are just going to use their WinAPI features to do what we do with ANSI escape sequences currently.

Snarkiness aside, the goal is to replace all ANSI escape codes (\0x1b prefixed stuff in all calls to printf) with the equivalent Windows API function call.

Allow other backends

  • Split the commandline class into frontend and backend
  • Implement a new backend for buffered input with no handling
  • Switch to this new backend if isatty() is false

Remove is_interactive() from InteractiveBackend

The InteractiveBackend is only used if is_interactive() returns true, so there's no need to check for that in the implementation anymore.

  • Remove is_interactive uses from InteractiveBackend

Move to C++11

The codebase does not require modern C++ (14, 17), as far as I can see. I'd like to see us move all code to C++11, and enforce this in the CMakeLists.

As a result, commandline can be integrated into more C++ projects.

Cursor left-right movement

This is partially supported already, just needs to be implemented. The idea is moving the cursor via left & right arrow keys. See m_cursor_pos for this.

Add prompts

Hi!

Nice library right here!

I wonder if it is possible to have some text prompting the user to input something.

GNU `screen -dmS` causes commandline to break and CPU spin

  1. Run commandline_test as screen -dmS test commandline_test
  2. Observe 100% CPU spin
  3. Attach via screen -r test and observe completely bugged input
  • screen -dmS should work as expected
  • there should be no CPU spin possible

Notes

  • it may be that isatty() changes after initialization(?)

Make delete key work

Currently, the delete key does not work. This wasn't implemented originally, because cursor movement didn't exist.

  • Find out what the escape sequence is for Delete on Windows+Linux
  • Implement removal of a character when Delete is pressed

Rewrite CMakeLists

The current CMakeLists has a few bad decisions, the wrong version requirement, and a few other issues.

Rewrite it to make it conform to a newer standard, while going down in required version number (to support older codebases, see #10).

History is broken on windows

When pressing Up-Arrow on the keyboard, the last entered command should appear. Pressing this repeatedly will go through all entered commands in the current session in reverse-chronological order. Down-Arrow then should do the opposite, ending up at the current prompt.

It doesn't do this properly on (all?) windows machines (CMD).

atexit woes

Hey, nice library. I am wondering if it makes sense to move the atexit function restoring termios to just the destructor of the commandline? I have a server that handles SIGINT in order to gracefully store stuff to disk and then immediately _exit in order to avoid having to tearing down multi-gigabytes of structures. Guess it's just one of those weird cases.

For now I am just calling the atexit handler in the destructor ๐Ÿ‘

CMP0037 - The target name "test" is reserved when CTest testing is enabled.

In CMakelists.txt - line 23.

if(BUILD_EXAMPLES)`
    add_executable(test main.cpp)
    target_link_libraries(test commandline)
    set_property(DIRECTORY ${CMAKE_SOURCE_DIR} PROPERTY VS_STARTUP_PROJECT test)
endif()

The target "test" is reserved and will cause cmake to fail configuration when CTest testing is enabled.

CMP0037

Suggest changing the target name.

Thank you for the commandline library!

Input line wrapping

The library should figure out how long the terminal line is (or similar) and wrap long lines properly. Currently, long input lines are mostly broken.

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