A-Shell’s differences
In this article, we will talk about three topics: a-Shell’s features, limitations, and comparison with alternatives.
Features
Shortcuts
This is one of the most welcomed functions of a-Shell. You can easily find the supported shortcuts on WorkFlow:
With WorkFlow, what you can do with a shell has been greatly expanded.
By default, all files generated by shortcuts are stored at ~shortcuts/.
Jump here and there
z command is built-in. With it you can easily jump between directories. What’s more, z is lighter and faster than autojump, making it more suitable for a-Shell.
Adding bookmarks for directories is also supported. Use bookmark <name> to add a bookmark for the current directory, cd ~<name> or jump <name> to jump to a bookmark, showmarks to show all current bookmarks, renamemark to revise the name of a bookmark and deletemark to delete it.
Any time you run cd without a parameter, you will be led to ~/Documents, the initial directory. cd - will lead you to the last directory you were in.
iOS/iPadOS interactions
A series of commands are provided to interact with other apps. Use open <file> to share a file with other apps:
Use view to view a file rapidly, which may be helpful for PDF/HTML files or images.
Use play command to play audio/video files.
Use internalbrowser like internalbrowser https://google.com to visit web pages within a-Shell, and swipe left or right to jump between pages. When you swipe right on the first page you view, you will go back to the console. This function may be helpful for front-end projects in the future.
Although you can easily share a file from a-Shell via open, you can’t share a file to a-Shell directly. Fortunately, you can achieve that using shortcuts. As mentioned earlier, all files shared to a-Shell are saved at ~shortcuts/. For another location, consider using a shortcut to execute a command automatically.
Use open tel://<phone number> to make a phone call with a-Shell, and use open sms://<phone number>&body=<msg content> to send a SMS message. Don't use the functions to spam others.
Access to the files
You can also read/write ~/Documents/ folder with Files. Switch to “My iPhone”/“My iPad”, and you’ll see the directory “a-Shell”. Attention files outside of ~/Documents/ can not be read.
Limitations
Limitations mainly come from two aspects: those from Apple and those from the FSF.
Limitations from Apple
Due to Apple’s limitation, only those directories can be accessed by a-Shell: ~/Documents/, ~/Library and ~/tmp, which has made a-Shell’s file structure uncommon. All user configuration files are stored at ~/Documents/ instead of ~, and $HOME has been set to ~/Documents/ as well. The file structure has made building works, especially cross-compiling more complex, so it should be treated carefully.
Executable files are either native codes for iOS/iPadOS, or WebAssembly files. Due to Apple’s limitation, all native codes must be shipped with the App itself when released. To add a new command with native codes, you have to resign the developer certificate and release the whole app to App Store, and all users would receive the update then.
For native codes, many functions are unavailable on arm64 for iOS, such as fork(), exec(), system(), etc. a-Shell emulates fork() and exec() for POSIX programs, which is not perfect but enough. WebAssembly is very limited as well, so that few commands can be compiled to WebAssembly.
sudo is also unavailable because of Apple’s limitations, so programs requiring a super-user privilege like traceroute does not work.
For jailbroken device users, there may be differences on a-Shell. For example, the entire file system would be able to read/write, which may cause problems. Do not hesitate to open an issue if you meet any of those!
Limitations from the FSF (Free Software Foundation)
There are actually many restrictions to use programs under GPL license. It may be not allowed to include GPL codes in the App Store distributions. You may have to ask for all contributors‘ permission, which may be very hard. Thus, it‘s suggested not to include any GPL codes in a-Shell and try to find alternatives under BSD or other licenses. bash, emacs, nano and many other excellent programs can’t be included for this reason.
Comparisons with alternatives
Here are comparisons between a-Shell and some alternatives. You may find which one suits you better here.
iSH
iSH is a Linux emulator for iOS/iPadOS, which uses syscall to translate Linux x86 commands. Of course, it’s interesting to use Alpine with an iOS device without jailbreaking.
With an emulating layer, iSH can do more things than a-Shell. You can run normal bash scripts, compile and run native binary codes or use apk to install a great number of packages. But attention iSH can’t do anything you like. node.js and some important tools can’t be supported. What’s more, iSH works greatly slower and more unstable than a-Shell. It’s not very happy to wait 10 seconds for a simple Python script or a minute to clone a Git repository, right?
Blink Shell
Blink is a remote device connecting tool for iOS/iPadOS, which now provides the best terminal experience on an iOS device. Blink Shell’s command function is based on ios_system, the same with a-Shell, so it’s listed here.
Blink Shell has an awesome appearance, an easy-to-use configure menu and a strong remote working ability, so it’s a recommended SSH/Mosh client for iOS/iPadOS. But Blink Shell itself is much weaker than a-Shell, where only basic UNIX commands are supported. You can’t even clone from a repository with it!
Blink Code is another welcomed function of Blink. Imagine coding with VSCode on an iPad everywhere! But attention it’s based on vscode.dev. Actually there is not a way to run a native VSCode on iPad yet.
Blink is not completely free of charge as well. Users of the free plan will receive a “it’s time to become a pro” screen every day. They are forced to “rest“ for a while and have to pay for the advanced plan to remove it.
NewTerm
NewTerm is a terminal app for Apple devices. For iPhones or iPads, jailbreaking is required. It’s a real terminal emulator that can control the Apple Device completely, which is welcomed by jailbroken users. Of course, the things it can do are much more than what a-Shell can do.
Besides functions, it has a tab-based interface and good font support. However, there are still some jailbroken users who prefer a-Shell for its shortcuts or other features.
Termux
Termux is a terminal emulator for Android devices, supporting Linux environments for them. It uses pkg to manage packages.
Based on the Linux sub system, Termux has a strong ability to run a lot of programs, no matter bash, zsh or fish. What’s more, a number of developing tools are built-in, allowing users to build or debug. It can also use the API of Android, like reading the SMS box.
It’s even amazing to provide proot to allow users to install a complete Linux system here, and then almost everything can be done. On the contrary, the number of what an iOS device can do is much smaller.
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