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From: Serbinenko Vladimir
Subject: Scripting
Date: Fri, 11 Feb 2005 23:01:31 +0100
User-agent: Mozilla Thunderbird 1.0 (X11/20041206)

Marco Gerards wrote:

I had a quick look at the patch for now.  Can you please explain in a
new thread how the patch globally works?  I will reply about the other
issues there as well.

There are still some things I would like to know:

- Why does everything happen with strings?

Because environment variables are the strings and it's not really
needed to convert them (excluding the calculating)

- Why are that many functions duplicated? (for example

In this case I just forgot about grub_strdup. But some other functions
have (nerly) the same names that string function but are adapted for
scripting (ex: grub_bash_strchr)

- What is that huge table with operators?
It's used to determinate which operator to execute (see
grub_bash_find_oper and grub_bash_eval_arith)

What kind of parser is it?
It's a direct parser with aritmetic subparser. Main parser is
grub_bash_execute, arithmetic subparser is grub_bash_eval_arith.
grub_bash_execute determinates the special cases (loops,conditions,
functions,...) for other cases (commands,assignments, function calling)
it calls grub_bash_split_tokens, grub_bash_expand_braces and

 I have never seen this in a top-down or bottom-up parser I have

I don't like to write the things reffering every time to algorithm.
Genereally I take some ideas and I write myself, at my own.

- How does the parser in general work?
grub_bash_execute parses a line. If it detectes that end of the line is
not the end of command it calls getline function

So can you explain what
 happens when executing a script?  First you load the file.  Do you
 parse it, make pcode of it, run it directly?

For the files I use grub_bash_exec_file. Only thing it does is
reading a file line by line and calling grub_bash_execute

 How about error

For now the problem is that not all posiible syntax errors are handled
correctly and more return checks have to be written. But first I'll write
line counting (only grub_bash_execute, grub_bash_list_execute and
grub_command_execute are affected)


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