Well in bash/sh the () means execute in a sub-shell. If you redirect or pipe output from one process to a command in a sub-shell it will be redirected or piped (whatever the original was) to the command being executed in the sub-shell.

You can also use $(command) as a command-line variable that will substitute the output of the command during evaluation.

Ie
# mkinitrd /boot/initrd-$(uname -r).img $(uname -r)

-Ross


-----Original Message-----
From: centos-bounces@centos.org <centos-bounces@centos.org>
To: CentOS mailing list <centos@centos.org>
Sent: Mon Nov 12 17:57:11 2007
Subject: Re: [CentOS] backups and md5 all in one while splitting

Ross S. W. Walker wrote:
>
> 'tee' splits the stdin into multiple output streams.
>
> The first instance of tee you listed gave it a file name and a pipe to
> output the stdout to.
>
> The second instance did a redirection to a sub-shell which then passed
> it to 'split' and it also had a pipe.
>
> -Ross
>

How does this sub-shell redirection work?  Can someone explain the
syntax to me or shoot me a link to a doc somewhere?

Russ

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