SYNTAX

Since the syntax of the Zoidberg shell is completely configable we can only comment on the syntax as defined by the default config files. The general structure will be the same for most user defined configuration but any markup or token could be changed to render the syntax completely unrecognizable.

The zoidberg syntax consists of three levels of grouping:

Logical grouping

First the syntax is split into blocks with logical/script delimitters

[block] && [block] || [block] ; [block]

Pipes and redirections

Once the string is cut into logical blocks each of these blocks is split in sub blocks by pipes and.

[sub_block] | [sub_block] | [sub_block]

Context blocks

At last for each of these sub-blocks a context is decided like:

SH	- sh like syntax (only very basic statements)
CMD	- builtin commands
PERL	- blocks of perl code

Each is executed differently by a suitable subroutine or application, and all are glued together to form a pipeline.

CONTEXTS

The contexts named below are hardcoded, others can be added by plugins. To disable hardcoded contexts see SETTINGS

FIXME how to link properly to this setting ?

PERL

Perl is the default context if the whole block is between curly brackets, when the first non-whitespace char of the block matches $,@ or % , or when the first word is a word that is reserved, like 'if', 'while', 'for' etc.

FIXME where are these configgable ?

# perl because of reserved word
zoid> for (0..3) { sleep 1; print $_ . "\n" }

# perl because of dollar sign
zoid> $self->{settings}{naked_zoid}++

# perl because of curlies
zoid> { open TEST, '<test.dat' }

Perl code can have modifyers after the last curly. Currently supported are :

n: enclose the expression in a "while STDIN" loop
p: like 'n' but also print $_ at the end of each loop
g: grep lines from STDIN that make the expression return non-zero

zoid> ls -al | { s/^(d)\S+/DIR:/ }g

# This will _NOT_ work -- each member of the pipeline is in a forked process :(
zoid> ls -al | { $i++ }n && { print "$i files" }

If you use the "naked" form (without the enclosing curlies) a bit of source filtering is applied redering a dereference operator -> with a whitespace in front of it into $self->.

# Thus
zoid> ->kill('1230')

# is the same as
zoid> $self->kill(1230')

FIXME what about the "poundsign namespace" ?

SH

This context is intended to make the zoidberg shell a little friendlier to people used to shells like bash(1). Also this syntax requires less chars to execute a system command. Only the most basic stuff is implemented, use perl for things like flow control. Since the default syntax for pipelines and logic lists is also the same as in sh-like shell, one can use basic commands in a naturla way.

# this does what it would in /.*sh/
zoid> ls -al | grep -v CVS | grep ^d > dirs.txt

Be aware redirections ain't fully supported

CMD

This context is not really distinguishable from the SH context, but it is used for builtin commands (perl subs that fake to be a system command). There was need for a seperate context for this so builtins won't have to fork (unless used in a pipeline) and thus can alter the parent environment.

FIXME

FIXME comment on custom defined contexts

FIXME comment on commands, aliases etc.

FIXME comment on redirections

Examples

Some system binary, context SH

zoid> mplayer -vo sdl -ao sdl my_favorite_movie.avi

Perl code between brackets, context PERL

zoid> { print "This is perl code." }

A subroutine call to an object loaded in zoidberg, context PERL but with a little source filtering applied.

zoid> ->Help->help
 -or-
zoid> ->Help->help('objects')

A builtin command faking to be executable, context CMD

zoid> cd ..

A custom syntax (SQL) enforced on a block:

zoid> sql{ SELECT * FROM users WHERE clue > 0 }

And as said all of these can be combined:

zoid> cd /usr/local && { print "This is perl code." } | less || sql{SELECT * FROM users WHERE clue > 0}

This will first execute cd /usr/local, on sucess followed by { print "This is perl code." } | less and if one of these failes we get to see the result of sql{SELECT * FROM users WHERE clue > 0}

This makes the precedence of this example as follows.

( ( 1 and ( 2 pipe 3 ) ) or 4 )

1 = cd /usr/local
2 = { print "This is perl code." }
3 = less 
4 = sql{SELECT * FROM users WHERE clue > 0}