Liquid prompt -- A useful adaptive Bash prompt

Liquid prompt is a smart prompt for the "Bourne-Again" Unix shell (bash).

The basic idea of the liquid prompt is to nicely display useful informations on the shell prompt, only when they are needed. It adds carefuly chosen colors to draw your attention on what differs from the normal context. Thus, you will notice what changes, when it changes, because you do not become accommodated to informations that are always displayed in the same way.

FEATURES

If there is nothing special in the current context, the liquid prompt is close to a default prompt:

[user:~] $

If you have ran one command in background that is still running and that you are in a git repository on a server, at branch "myb":

1r [user@server:~/liquidprompt] myb ±

A liquid prompt displaying everything may look like this:

⌁24% ⌂42% 3d/2&/1z [user@server:~/ … /code/liquidprompt]↥ master(+10/-5,3) 125 ±

It displays:

the average of the batteries remaining power, if it is under a given threshold, with a colormap too;
the average of the processors load, if it is over a given limit, with a colormap that became more and more noticeable with increasing load;
the number of detached sessions (screen), if there is any;
the number of attached sleeping jobs (when you interrupt a command with Ctrl-Z and bring it back with fg), if there is any;
the number of attached running jobs (commands started with a &), if there is any;
the current user, in bold yellow if it is root, in light white if it is not the same as the login user;
the current host, if you are connected via an SSH or telnet connection, with different colors for each case;
a green colon if the user has write permissions on the current directory, a red one if he has not;
the current directory in bold, shortened if it takes too much space, while preserving the first two directories;
an up arrow if an HTTP proxy is in use;
the name of the current branch if you are in a version control repository (git, mercurial or subversion), in green if everything is up to date, in red if there is changes, in yellow if there is pending commits to push;
the number of added/deleted lines, if changes have been made and the number of pending commits, if any;
the error code of the last command, if it has failed in some way;
a smart mark: ± for git directories, ☿ for mercurial, ‡ for svn, $ for simple user, a red # for root.

You can temporarily deactivate the liquid prompt and come back to your previous one by typing prompt_off. Use prompt_on to bring it back. You can deactivate any prompt and use a single mark sign ($ for user and # for root) with the prompt_OFF command.

INSTALL

Include the file in your bash configuration, for example in your .bashrc:

source liquidprompt.bash

Copy the liquidpromptrc-dist file in your home directory as ~/.config/liquidpromptrc or ~/.liquidpromptrc and edit it according to your preferences. If you skip this step, the default behaviour will be used.

DEPENDENCIES

Apart from obvious ones, some features depends on specific commands (if you want a git support you'd better install git…):

battery status need acpi,
detached sessions is looking for screen.

For other features, the script uses commands that should be available on a large variety of unixes: tput, grep, awk, sed, ps, who.

PUT THE PROMPT IN A DIFFERENT ORDER

You can configure some variables in the ~/.liquidpromptrc file:

LP_BATTERY_THRESHOLD, the maximal value under which the battery level is displayed
LP_LOAD_THRESHOLD, the minimal value after which the load average is displayed
LP_PATH_LENGTH, the maximum percentage of the screen width used to display the path
LP_PATH_KEEP, how many directories to keep at the beginning of a shortened path
LP_REVERSE, choose between reverse colors (black on white) or normal theme (white on black)
LP_HOSTNAME_ALWAYS, choose between always displaying the hostname or showing it only when connected with a remote shell

You can sort what you want to see by exporting the LP_PS1 variable, using the variables you will found in the __set_bash_prompt function.

For example, if you just want to have a liquidprompt displaying the user and the host, with a normal path in blue and only the git support:

export LP_PS1=`echo -ne "[\${__USER}\${__HOST}:\${BLUE}\$(pwd)\${NO_COL}] \${__GIT} \\\$ "`

Note that you need to properly escape dollars in a string that wil be interpreted by bash at each prompt.

To erase your new formatting, just bring the LP_PS1 to a null string:

 export LP_PS1=""

KNOWN LIMITATIONS AND BUGS

Liquid prompt is distributed under the GNU Affero General Public License version 3.

Cannot easily change the colors of features having different state colors (like the colormap of the load or the colors of the branch name).
detached sessions only looks for screen, a tmux support would be nice…
Does not display the number of commits to be pushed in Mercurial repositories.
Subversion repository cannot display commits to be pushed, this is a limitation of the Subversion versionning model.
The proxy detection only uses the $http_proxy environment variable.

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