Cicada Unix Shell

Cicada is a simple Unix shell written in Rust. It's ready for daily use.

Documents

• Environment Variables
• Built-in Commands
• Completion
• RC File
• History

Features

run programs and pipelines

$ ls | head -n3
Desktop
Documents
Downloads

$ echo foo bar | awk -F " " '{print $2, $1}'
bar foo

with redirections

$ ls file-not-exist 2>&1 | wc > e.txt
$ cat e.txt
       1       7      46

command substitution

$ ls -l `which sh`
-r-xr-xr-x  1 root  wheel  630464 Mar 23 07:57 /bin/sh

run multiple commands (with logical)

$ echo foo; echo bar
foo
bar

$ echo foo && echo bar
foo
bar

$ echo foo || echo bar
foo

shell expansions

$ echo sp{el,il,al}l
spell spill spall

$ echo $SHELL
/usr/local/bin/cicada

$ echo *
Cargo.lock Cargo.toml LICENSE Makefile README.md src target

do math arithmetic directly in the shell!

$ 1 + 2 * 3 - 4
3
$ (1 + 2) * (3 - 4) / 8.0
-0.375

Install Cicada

Note: Rust environment is needed for installation.

You can try cicada out without installing it by checking out the repository and run cargo run in its root directory.

$ git clone https://github.com/mitnk/cicada
$ cd cicada
$ cargo run

install from code repository

If you've checked out the cicada repository, you can do this:

$ make install

This will install cicada under your /usr/local/bin. Use sudo if needed.

install via cargo crates

$ cargo install -f cicada

This will install cicada into ~/.cargo/bin/.

Set cicada as your login shell

Appending /usr/local/bin/cicada into your /etc/shells, then run

$ chsh -s /usr/local/bin/cicada

FAQs

Why another shell?

• for fun
• to learn Rust
• have a shell that can customize a bit for my own needs

I think it's fair to say cicada is just a toy.

Compare to bash?

Bash is where most people come from and familiar with. So cicada is trying to support common cases that bash supports. Cicada will only be a "subset" of bash. If bash is a steamship, cicada is just a boat.

Compare to ion?

Ion is a modern system shell that is also written in Rust. It's more mature as a general shell. Ion is to Rust what xonsh to Python, which supports following stuff:

$ let string = "one two three"
$ echo $string[0]
o
$ echo $string[..3]
one

While cicada do not and will not support these features.

Why functions support is in won't do list?

I don't think i have interests or energy to add (bash) functions support or (bash) shell scripting ability. If you're a heavy function/scripting user, cicada may not be your tool. If you found cicada useful, you can always add your things based on it.

As far as I can see, cicada will not introduce such complex things, and will not be another zsh/fish.

Will cicada be POSIX-compatible?

As the above anwsers hints, while cicada is trying to be POSIX, but it will not be a fully POSIX shell. However, If any command pattern is common and cicada is missing, we can add it.

Will my bash/zsh scripts continue work in cicada?

It depends. If the script is only doing external things, like an configure/installation script, you can still run it. You can invoke scripts with $ ./my-script.sh as long as it have "#!/bin/bash" stuff on the top. Or you can always run them as: $ bash my-script.sh.

Cicada does not recognize these scripts itself. You cannot integrate these shell scripts/functions in RC files to initiate cicada shell.

Windows support?

I personally do not have a Windows box to work on, and cicada use a lot of Unix/Linux specific things internally. But you can fork it and play it with Windows maybe if you want to.

To do list

• job controls (Ctrl-Z, fg, bg etc)
• and less...

Won't do list

• functions
• Windows support
• and more...