Env::PS1(3) prompt string formatter


# use the import function
use Env::PS1 qw/$PS1/;
$ENV{PS1} = '\u@\h \$ ';
print $PS1;
$readline = <STDIN>;
# or tie it yourself
tie $prompt, 'Env::PS1', 'PS1';
# you can also tie a scalar ref
$format = '\u@\h\$ ';
tie $prompt, 'Env::PS1', \$format;


This package supplies variables that are ``tied'' to environment variables like 'PS1' and 'PS2', if read it takes the contents of the variable as a format string like the ones bash(1) uses to format the prompt.

It is intended to be used in combination with the various ReadLine packages.


You can request for arbitrary variables to be exported, they will be tied to the environment variables of the same name.


When you "tie" a variable you can supply one argument which can either be the name of an environment variable or a SCALAR reference. This argument defaults to 'PS1'.


Returns the formatted string.

Using this method all the time is a lot less efficient then using the tied variable, because the tied variable caches parts of the format that remain the same anyway.


The format is copied mostly from bash(1) because that's what it is supposed to be compatible with. We made some private extensions which obviously are not portable.

Note that this is not the prompt format as specified by the posix specification, that would only know ``!'' for the history number and ``!!'' for a literal ``!''.

Apart from the escape sequences you can also use environment variables in the format string; use $VAR or "${VAR}".

The following escape sequences are recognized:

The bell character, identical to ``\007''
The date in ``Weekday Month Date'' format
The date in strftime(3) format, uses POSIX
The escape character, identical to ``\033''
Carriage return
The basename of $0
The current time in 24-hour format, identical to ``\D{%H:%M:%S}''
The current time in 12-hour format, identical to ``\D{%I:%M:%S}''
The current time in 12-hour am/pm format, identical to ``\D{%I:%M %p}''
The current time in short 24-hour format, identical to ``\D{%H:%M}''
The username of the current user
The current working directory
The basename of the current working directory
``#'' for effective uid is 0 (root), else ``$''
The character corresponding to the octal number 0dd
Literal backslash
Hostname, uses Sys::Hostname
First part of the hostname
The basename of the (output) terminal device name, uses POSIX, but won't be really portable.
\[ \]
These are used to encapsulate a sequence of non-printing chars. Since we don't need that, they are removed.


The following escapes are extensions not supported by bash, and are not portable:
The (output) terminal device name, uses POSIX, but won't be really portable.
Insert the ANSI sequence for named colour. Known colours are: black, red, green, yellow, blue, magenta, cyan and white; background colours prefixed with ``on_''. Also known are reset, bold, dark, underline, blink and reverse, although the effect depends on the terminla you use.

Unless you want the whole commandline coloured you should end your prompt with ``\C{reset}''.

Of course you can still use the ``raw'' ansi escape codes for these colours.

Note that ``bold'' is sometimes also known as ``bright'', so ``\C{bold,black}'' will on some terminals render dark grey.

If the environment variable "CLICOLOR" is defined but false colours are switched off automatically.

Proc information.

All of these are unix specific

Acpi AC status '+' or '-' for connected or not, linux specific
Acpi battery status in mWh, linux specific
Load average
First number of the load average
Acpi temperature, linux specific
Number of users logged in

Not implemented escapes

The following escapes are not implemented, because they are application specific.
The number of jobs currently managed by the application.
The version of the application.
The release number of the application, version + patchelvel
The history number of the next command.

This escape gets replaced by literal '!' while a literal '!' gets replaces by '!!'; this makes the string a posix compatible prompt, thus it will work if your readline module expects a posix prompt.

The command number of the next command (like history number, but minus the lines read from the history file).


If you want to overload escapes or want to supply values for the application specific escapes you can put them in %Env::PS1::map, the key is the escape letter, the value either a string or a CODE ref. If you map a CODE ref it normally is called every time the prompt string is read. When the escape is followed by an argument in the format string (like "\D{argument}") the CODE ref is called only once when the string is cached, but in that case it may in turn return a CODE ref.


Please mail the author if you encounter any bugs.


Jaap Karssenberg || Pardus [Larus] <[email protected]>

This module is currently maintained by Ryan Niebur <[email protected]>

Copyright (c) 2004 Jaap G Karssenberg. All rights reserved. Copyright (c) 2009 Ryan Niebur. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.