Configure the Shell
This article focus on configuring the shell of a-Shell. The default (and the only) shell on a-Shell is not bash, but dash. There are differences between a-Shell’s default shell (the shell you see when you start the App) and dash (the shell to execute scripts) and you can run dash to see how dash works.
Why dash?
It’s a difficult task to include a shell in a-Shell. Among the various shells we can choose, dash is a simpler and lighter one.
Although bash is used more commonly, it can‘t be included in a-Shell, because it’s under GPL. zsh is much more complex, but it’s on the to-do list. If it can be included successfully, the user’s experience would be greatly improved.
Execute scripts
As dash is POSIX-compatible, standard shell scripts are able to be executed. But one thing should be noticed: a number of scripts relies on bash actually. The first lines of some scripts is not /usr/bin/env sh but /usr/bin/env bash, making it not work, even including original neofetch. You can try to change bash to dash or sh, but all scripts using the features of bash won’t work anyway. In many cases you have to rewrite the script to avoid that. This may be improved if zsh can be added in the future.
A Perl script checkbashisms is available to check if your script is compatible with a-Shell. First ensure your script starts like #!/usr/bin/sh (which means runs with most POSIX-compatible shells), and then use checkbashisms to check if non-compatible grammars are used:
# If you have not installed it before, do it first.
pkg install checkbashisms
# Then check it.
checkbashisms [your_script].profile and .bashrc
~/Documents/.profile and ~/Documents/.bashrc are provided to let you define what to do when the shell starts. When a new a-Shell window starts, both ~/Documents/.profile and ~/Documents/.bashrc are loaded, and when dash starts, only ~/Documents/.profile is loaded. That’s the difference between them. You can add many things to the two scripts: environment variables, alias, the prompt, etc. For example, add a alias to your .profile:
alias md='mkdir'Define the prompt
Zsh lovers may be addicted to the colorful prompts of the terminal. The good news is that you can also change what the prompt looks like on a-Shell, but it’s not as easy as how you “set a theme” on zsh or fish.
What the prompt looks like is defined by the variable $PS1. For example, you can set it to a character you like:
Sometimes we want to know the current path or other useful information via the prompt. Here are some parameters you can use:
\d: the current date\u: the username stored at$USERNAME,mobileby default\s: the shell’s name: the end of a line, used to start a new line
: the current time, going by hh:mm:ss and 24-hour format
: the current time, going by hh:mm:ss and 12-hour format
\@: the current time, going by hh:mm and 12-hour format\A: the current time, going by hh:mm and 24-hour format\v: the current version of a-Shell\V: the current version and build number of a-Shell\w: the current complete path\W: the current working dictionary, not the complete path\!and\#: the number of the command, not working correctly now\$: judge if the account isroot,#if yes while$if no (it won’t be yes even if you‘ve jailbroken)\\: a backslash\[and\]: start or stop a place of non-printed characters, which is used to define controlling characters like changing the color
You can use ANSI controlling characters to define colors or other styles. Here is an example:
Add the command to .bashrc so that it can be loaded every time a-Shell starts.
Now guess how to get a rainbow-style prompt like this. Nerd fonts will be needed for arrays.
Attention this feature only works for a-Shell’s default shell (the one when a-Shell starts) but not for dash. When you run dash, you can only get a series of strange codes.
You may want to add a command to the variable like `pwd`. However, it doesn’t work with a-Shell, so you can’t see git status on the prompt.
Define colors of ls
This part is planned.
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