[jamming] jam shell

[Mildred]

Hi,

I just spent 5 hours modifying ft-jam to create a jam-shell. It is a
shell language (not meant to be used interactively, only in scripts).
Actually it is very basic, but promising from my point of view.

Basicly, I just removed the 'actions' statement and the execution of
the actions after rules are parsed. Unknown rules are understood as
external program invocation, and few builtins rules were added.

special variables:
	$(...)		arguments to the script
	$(?)		return status of the last command
	$(!)		pid of the last command run in background

Special rules:

	Ex command line ;
		Execute the "command" program with the parameter
		"line". It is used to be able to call programs that
		have the same name as builtins rules.

	Export variable := value ;
		Export the variable named "variable" to the environment
		giving the value "value". Force the assignment.

	Export variable ?= value ;
		Export the variable named "variable" to the environment
		giving the value "value". If the variable already
		exists in the environment, it is not erased.

	Export variable =! ;
	Export variable ;
		Delete the variable named "variable" from the
		environment.

The following rules have been kept from Ft-Jam:
	Echo, Exit, Glob, Match, Command, Split

It is possible to run a command in background with the following syntax:

	command arg1 arg2 : "&" ;
or	Ex command arg1 arg2 : "&" ;


What should come next :

	read from the terminal (read)
	wait for childs (started with "&")
	redirect std{in,out,err} of commands
	modify environment variables on command invocation (execve)

You can see the source code here:
https://code.launchpad.net/~mildred/+junk/jam-shell


Do you think it is a good idea ? My main motivation for that was to get
rid of the wwierd variable expansion of sh and compatible shell that
forces you to write "$var" (in quotes) to be shure that spaces in the
variable won't split the argument of the command. Moreover i like the
Jam language so much that i thought I had to do something like that.
And it was easy.

Enough for now, it is 3 AM ... good night

Mildred

-- 
Mildred Ki'lya
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