NAME

psh - Developing for Perl Shell

SYNOPSIS

Developing for the Perl Shell.

DESCRIPTION

DEBUGGING

The -d option puts psh into "debugging" mode, which prints diagnostic output. Note that you can also enter/leave this debugging mode in a running psh via the $Psh::debugging variable.

Possible values for -d/$Psh::debugging are either 0 to disable it, 1 to enable all debug messages or a string of characters where each character denotes a certain class of debug messages.

"s" - enables printing of information about the chosen strategy for each command
"o" - enables printing of "other" debug info - info which has not been further categorized
"f" - enables printing of the rc files read by psh on startup while it is executed and allows easy tracing of problems in these files
"i" - enables printing of initialization debug info
"e" - enables printing of otherwise suppressed error messages
"c" - enables printing of debug messages for completion

Even though psh aims to be an interactive shell instead of a scripting environment, speed is important. The main concern here is that startup speed of psh, which is primarily determined by two factors:

perl startup and module loading
command processing speed

The startup time on a normal, not to busy, computer should be smaller than one second. To make this possible, keep some simple rules in mind:

prefer "require" to "use" whenever possible
delay loading modules until they are really needed
let the "applies" method of evaluation strategies be as fast as possible

BUILT-IN FUNCTIONS

On startup, "psh" scans the Psh::Builtins:: namespace and will add the names of all found dynamic loadable builtins to %Psh::built_ins.

During evaluation of an input line, "psh" will first check the %Psh::built_ins variable. If this fails it will try to locate an appropriate built-in function in Psh::Builtins.pm.

A dynamical loadable builtin has to be in a file called Builtinname.pm within the Psh::Builtins:: namespace and has at least one subroutine, called 'bi_builtinname'. Additionally, it may provide a cmpl_builtinname subroutine for a custom completion. Furthermore, a builtin should contain some pod documentation, starting with "=item * " and ending with "=cut". The builtin will be called with 2 arguments, the first one if the rest of the line while the second one is an array to all the words psh discovered.

For a list of the predefined psh builtins, use the "help" command from within psh.

DEFINING EVALUATION STRATEGIES

Currently empty due to overhaul of strategies