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Date: Wed, 19 Dec 2012 22:04:18 +0100
From: Jilles Tjoelker <jilles@stack.nl>
To: d@delphij.net
Subject: Re: svn commit: r244198 - in head: etc/rc.d sbin/sysctl
Message-ID: <20121219210418.GA83983@stack.nl>
References: <201212132332.qBDNWmK4037503@svn.freebsd.org>
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Cc: Ian Lepore <freebsd@damnhippie.dyndns.org>,
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On Wed, Dec 19, 2012 at 11:16:26AM -0800, Xin Li wrote:
> It may be worthy to make sysctl(8) to accept mutiple -f's, but it
> seems to be hard to write shell scripts that utilizes this feature in
> a elegant manner.

This is possible but indeed a bit ugly.

Hard-coding the list of files is not too bad:

shift $#
for _f in /etc/sysctl.d/* /etc/sysctl.conf /etc/sysctl.conf.local; do
	[ -r "$_f" ] && set -- "$@" -f "$_f"
done
sysctl "$@"

If the list is passed in the positional parameters it becomes uglier:

_first=1
for _f do
	[ -n "$_first" ] && shift $#
	_first=
	[ -r "$_f" ] && set -- "$@" -f "$_f"
done
sysctl "$@"

This uses for's temporary storage of the words being iterated over,
building a new set of positional parameters in the loop.

An alternative is to append the new list to the old one and to use a
saved copy of $# to remove the old elements afterwards.

It would be nice to store the arguments in a variable but that is not
possible because all characters are valid in pathnames, except the null
character which cannot be used in shell either.

-- 
Jilles Tjoelker