From: Ronald Fischer <ronaldf@...>
Date: 2006-08-01T17:20:25+09:00
Subject: Default shell for Kernel::system() ?

Ist it possible to kind of define a default shell which will be used
for Kernel::system? I often need to invoke from my Ruby scripts
external commands, involving redirection and globbing, for example
(bash syntax)

    foo [a-z]* 2>&-
    bar <<<baz

etc. Since these syntactic elements are shell specific, I need to
specify the shell somehow, for example:

    system("bash --norc -c 'foo [a-z]* 2>&-'")
    system("bash --norc -c 'bar <<<baz'")

which is a bit cumbersome. Of course one obvious solution would be
to define a new function:

    def bash(cmd)
      system("bash --norc -c '"+cmd+"'")
    end

And use instead

    bash('foo [a-z]* 2>&-')
    bash('bar <<<baz')

But this solution has two drawbacks:

First one has to pay special attention that the shell command itself 
should no contain single quotes. For example, it is all too tempting
to write a call

    bash("my_command 'one argument'")

which looks correct at first sight, but will have a different
effect than

    bash('my_command "one argument"')

due to the interference between Ruby- and bash quoting.

Another drawback of this solution is that one has to include the
definition of the "bash" function with each Ruby script.

So I wonder whether there is may be a simple, builtin solution
for this problem - say, a way to specify the "default shell" used
for system().

Ronald

-- 
Ronald Fischer <ronaldf@eml.cc>
Posted via http://www.newsoffice.de/