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https://github.com/b-jure/ashe

UNIX async shell
https://github.com/b-jure/ashe

async c shell unix unix-shell

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UNIX async shell

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README 

        
# About

`ashe` is a simple **unix** single threaded (a)synchronous(she)ll written in C (not POSIX compliant).



It supports job control, all of the redirections, pipelines, conditionals, variable

expansion and other basic stuff you would find in `bash` or `fish-shell`.



Shell can recognize terminal lines allowing you to navigate input across terminal

lines rather than moving multiple lines in case input wraps across multiple

terminal lines.

This means `ashe` only works with terminals that wrap text.



It uses no dependencies (such as `curses`/`ncurses`) and is written to be compatible

with `C99`.



That being said this shell was made primarily for educational purposes and thus it lacks

in various features and many other functionalities you would expect from the more popular

shells.



## Build/Install

Before building/installing you can configure the build parameters in

`config.mk` and you can configure shell parameters in `src/aconf.h`.



Building from source using [GNU make](https://www.gnu.org/software/make/):

```sh

git clone https://github.com/b-jure/ashe 

cd ashe

make

```

Installing:

```sh

make clean && sudo make install

```



## Default Keybinds

List of default keybinds and actions:

- `Backspace`, `Delete` - delete character

- `End`, `Ctrl + e`     - move to end of the terminal row

- `Home`, `Ctrl + s`    - move to start of the terminal row

- `Left`, `Ctrl + h`    - move cursor to the left

- `Down`, `Ctrl + j`    - move cursor down one terminal row

- `Up`, `Ctrl + k`      - move cursor up one terminal row

- `Right`, `Ctrl + l`   - move cursor to the right

- `Ctrl + n`            - traverse history forwards (next)

- `Ctrl + p`            - traverse history backwards (previous)

- `Ctrl + r`            - clear screen (keeps scroll-back)

- `Ctrl + w`            - delete text behind the cursor

- `Ctrl + d`            - delete text in front of the cursor

- `Ctrl + x`            - exits the shell (full cleanup)



**Note:** in case redrawing bugg occurs just clear the screen (`Ctrl+r`),

if that doesn't fix it just send SIGINT (`Ctrl+c`).



## Shell syntax

List of all syntax symbols and their meaning.

Optional parameters are enclosed in `[]`.



- `c1 && c2` - conditional AND; list of sequences of one or more pipelines, the right command

`c2` is executed only if `c1` returns exit status of zero (`success`).



- `c1 || c2` - conditional OR; list of sequences of one or more pipelines, the right command

`c2` is executed only if `c1` returns non-zero exit status.



- `[ln]<&[n]` - duplicates descriptor open for reading; descriptor gets opened (duplicated) on

the number provided on the left side of the expression `ln`, if descriptor number `n` is not

provided on the right side of the expression descriptor number `1` will be used. 

This can also close descriptor number `ln` if `-` is provided on the right side of the expression

instead of the descriptor number `n`. 



- `[ln]>&[n, filepath]` - duplicates descriptor open for writing; descriptor gets opened (duplicated)

on the number provided on the left side of the expression `ln`, if descriptor number `n` is

not provided on the right side of the expression descriptor number `1` will be used.

This also closes descriptor `ln` if `-` is provided on the right side of the expression

instead of the descriptor number `n`. 

Additionally if both `ln` and `n` are absent then the behaviour is identical to

`&>` and the file provided by the `filepath` will be used instead.



- `>>filepath` - redirects `stdout` **appending** it into the file provided by the `filepath` on

the right side of the expression.



- `&>filepath` - redirects `stdout` and `stderr` into the file provided by the `filepath` on

the right side of the expression.



- `&>>filepath` - redirects `stdout` and `stderr` **appending** it into the file provided by

the `filepath` the right side of the expression.



- `[n]<>filepath` - opens the file provided by the `filepath` on the right side of the expression

both for reading and writing on file descriptor on the left side of the expression. If

`n` is not specified descriptor `0` is used instead.



- `[n]filepath` - opens the file provided by the `filepath` to be opened for writing

on file descriptor `n`, in case `n` is not provided, descriptor number `1` is used.



- `;` - separates pipeline lists. Generally used as a separator or can be used as indicator

that the command is being run in the foreground.



- `cmd (cmd)` - command reordering; command in `()` gets executed first and it's output is

piped into the input of `cmd` that is before it. Identical to the pipeline `|`.



- `|` - pipeline. Sequence of one or more commands separated by `|`. The output of each command

in the pipeline is connected via a `pipe(2)` to the input of the next command.



- `c1&` - runs command `c1` in the background (asynchronously) so the shell won't wait for the

command to be finished executing.



- `$var_name` - expands environmental variables in this example the `var_name`. The only way to

prevent this expansion would be to escape the `$` like this `\$`.



- `""` - quotes are used in order to write multi-line text and escape reserved symbols shell uses.

**Note** that `$` will still expand variables inside of quotes.



- `>|` - noclobber. NOT IMPLEMENTED but mentioned in the source files!



## Builtin commands

List of builtin commands:

- `cd` - change current directory.

- `pwd` - print working directory.

- `clear` - clear screen (and scrollback).

- `builtin` - list builtin commands.

- `fg` - move job/s into foreground.

- `bg` - move job/s into background.

- `jobs` - list jobs, their metadata and their status.

- `exec` - open/close/copy file descriptors and/or execute a command.

- `exit` - exit the shell.

- `penv` - print environmental variable/s.

- `senv` - set environmental variable.

- `renv` - remove environmental variable.



## Configuration

Configuration is done inside of `aconf.h` header file in `src` directory before

compiling/building the shell.