[U-Boot] [PATCH 2/2] env: add regex support for environment variables
Detlev Zundel
dzu at denx.de
Mon Nov 7 12:07:42 CET 2011
Hi Wolfgang,
this really is an interesting addition!
> Syntax: env regex [-g] [-s subst] regex name [...]
>
> The code is based on SLRE (http://slre.sourceforge.net/)
> which provides a tiny subset of Perl regular expressions.
>
> Without options, this will implement regex pattern matching on
> environment variables. Variables with matching values will be printd
> as with "env print", so this basicly performs a "grep" on the given
> list of variables.
Ok, this usage looks fine.
> With "-s subst", the matching pattern gets replaced with the string
> given in "subst". Back references '\0' ... '\9' are allowed, where
> '\0' stands for the whole matched string, and '\1', '\2', ... are
> replaced with the first, second, ... sub-pattern.
>
> "-g" allows for global replacement.
But IMHO this usage doesn't really belong into the "env" command. It
much rather is a further operation of the setexpr command:
set environment variable as the result of eval expression",
name value1 <op> value2\n"
- set environment variable 'name' to the result of the evaluated\n"
express specified by <op>. <op> can be &, |, ^, +, -, *, /, %"
We could add the <op>erations for regsubst and regsubstg. For actual
names for the operations, I'm somewhat unsure. Maybe "function like",
i.e. "regsubst(string, pattern, replacement)" and "regsubstg(string,
pattern, replacement)"?
> Examples:
> => setenv foo abcdefghijklmnop
> => env reg 'A' '[bdgmo]' foo
> => env reg -s 'A' '[bdgmo]' foo
> foo=aAcdefghijklmnop
> => env reg -g -s 'B' '[bdgmo]' foo
> foo=aAcBefBhijklBnBp
> => env reg -g -s '\\2--\\1' '(Be).*(kl)' foo
> foo=aAckl--BeBnBp
So I'd vote for
=> setenv result regsubst($foo, '[bdgmo]', 'A')
What do you think?
Cheers
Detlev
--
To you I'm an atheist; to God, I'm the Loyal Opposition.
-- Woody Allen
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DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel
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