NAME

psh - Developing for Perl Shell

COPYRIGHT

Copyright (C) 1999-2000 Gregor N. Purdy. All rights reserved. This script is free software. It may be copied or modified according to the same terms as Perl itself.

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

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

There are two hashes, %Psh::strategy_which and %Psh::strategy_eval. An evaluation strategy called "foo" is implemented by putting a subroutine object in each of these hashes keyed by "foo". The first subroutine should accept a reference to a string (the exact input line) and a reference to an array of strings (the array of "words" in the input line produced by &Psh::decompose, provided as a convenience so that each individual strategy doesn't have to recompute this). It should return a string, which should be empty if the strategy does not apply to that input line, and otherwise should be an arbitrary non-null string describing how that strategy applies to that line. It is guaranteed that the string passed in will contain some non-whitespace, and that the first string in the array of words is non-empty.

The $strategy_eval{foo} routine accepts the same two first arguments and a third argument, which is the string returned by $strategy_which{foo}. It should do the evaluation, and return the result. Note that the $strategy_eval function will be evaluated in an array context.