zaufi / smart-prompt

Smart bash prompt: easy way to show various context info in a command prompt

What Is This?

Smart bash prompt is a pluggable system to show various context information in a command prompt. The initial idea was to create an extensible engine to have a dynamically changing command prompt instead of a boring static one, capable of displaying some aux info depending on a particular location and/or condition.

For example, if you are in Git working copy, your command prompt will look like this:

zaufi@gentop〉 /work/GitHub/smart-prompt〉 :master〉 $

for /boot it'll be like

zaufi@gentop〉 /boot〉 3.10.9-gentoo-z1〉 3 days, 13:15〉

for my /usr/src/linux

zaufi@gentop〉 /usr/src/linux〉 -> linux-3.10.10-gentoo〉

and so on...

The system consists of two different parts:

• a pluggable engine, which loads context checkers and forms the resulting PS1;
• a context checker is a small script to display particular info in a command prompt depending on conditions.

bash Bindings

Except for changing a command prompt, this package also provides some keyboard macros for bash. Most of them targeted to KDE's konsole, but one may easily change key codes for any other terminal. To get a key code for a particular combination, press Ctrl+V in a bash prompt, then a desired key sequence. The other way is to run read and press whatever you want.

How To Install

As one may notice cmake is needed to install (or make source tarball of) this package. Replace the very first command with git clone https://github.com/zaufi/smart-prompt.git to get sources from the GitHub repository:

$ tar -zxf smart-prompt-X.Y.Z.tar.gz
$ cd smart-prompt-X.Y.Z
$ cmake -DCMAKE_INSTALL_PREFIX=/usr .
$ sudo make install

If you are brave enough you can copy needed files to their locations.

But to work, it doesn't require any other dependencies, except bash (and some tools detected at configure stage) -- cuz it is written using pure bash, nothing else ;-)

Note: To make bash bindings to work do not forget to append $include /etc/smart-prompt.inputrc to /etc/inputrc or ~/.inputrc.

Configuring

There is a system-wide config file /etc/smart-prompt.conf and the user one ~/.config/smart-promptrc. And finally, the user may override some settings depending on the current terminal in the ~/.config/smart-promptrc.${TERM} file.

The non-comprehensive list of options declared in the system-wide config file.

Almost every segment in a prompt has the color setting. To get the configuration variable responsible for the segment one can set SP_DEBUG=1 variable to get some "debugging" information.

Context Checker Details

Context checkers are searched in the following directories:

• [INSTALL_PREFIX]/libexec/smart-prompt/context-checkers.d
• ~/.config/smart-prompt.d

Context checker is a simple script aimed to do the two things:

• check if the current context is suitable to display some extra info;
• add some additional info to the PS1.

Context checkers should be named in the following format:

NNname.sh

where NN is a numeric value of a loading priority.

Typical context checker consists of two functions:

• predicate to decide whether some aux info should be displayed. It must return numeric code, where 0 stands for true and false is everything else. It must be named according to the following format: _NN_some_name, where NN same (or close to) as the number in the file name. This needed to preserve order in which checkers will be applied/tried.
• the second function should printf (it can do echo as well, but I don't recommend this due to some limitations) any aux info, it wants to put to PS1. It can use colors (ANSI escape sequences). See particular context checker for details (most of them are trivial and straightforward).

Finally, a checker module should register provided functions. To do so, near the end of any checker module, you may find the following:

function _NN_some_name() { return ... }

function _show_some_aux_info()
{
    printf "smth"
}

SMART_PROMPT_PLUGINS[_NN_some_name]=_show_some_aux_info

SMART_PROMPT_PLUGINS is a global associative array, where the key is a predicate to check, and the value is a function to execute.

Context checker can (re)use helper functions (API) defined in smart-pointer-functions.sh.

Limitations

• Nowadays I don't care about colorless terminals...

TODO

• Make prompt segments configurable per directory. For example, it could be an XML file rendered (and cached) into a final bash script to display prompt;
• Add cache to some segments and dirs;
• Themes.

Known Limitations

• Nowadays I don't really use (care 'bout) prompts w/ non-default background color.