Date: Mon, 10 Sep 2001 09:35:24 -0700 From: Ulf Zimmermann <ulf@Alameda.net> To: Adrian Filipi-Martin <adrian@ubergeeks.com>, Ulf Zimmermann <ulf@Alameda.net>, hackers@FreeBSD.ORG Subject: Re: Question about what programs to use in /etc/rc* Message-ID: <20010910093524.D1500@seven.alameda.net> In-Reply-To: <20010910181954.G1983@ringworld.oblivion.bg>; from roam@ringlet.net on Mon, Sep 10, 2001 at 06:19:54PM %2B0300 References: <20010910110537.A2053@ringworld.oblivion.bg> <20010910102943.N36056-100000@lorax.ubergeeks.com> <20010910181954.G1983@ringworld.oblivion.bg>
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On Mon, Sep 10, 2001 at 06:19:54PM +0300, Peter Pentchev wrote:
> On Mon, Sep 10, 2001 at 11:03:41AM -0400, Adrian Filipi-Martin wrote:
> > On Mon, 10 Sep 2001, Peter Pentchev wrote:
> >
> > > On Sun, Sep 09, 2001 at 06:06:01PM -0400, Adrian Filipi-Martin wrote:
> > > > On Sun, 9 Sep 2001, Ulf Zimmermann wrote:
> > > >
> > > > > These are some examples strings:
> > > > >
> > > > > "dhcp"
> > > > > "dhcp media 10baseTX"
> > > > > "media 10baseTX dhcp mediaopt half-duplex"
> > > > >
> > > > > The following code will get me inside a if condition:
> > > > >
> > > > > if [ `expr "${ifconfig_args}" : '.*[Dd][Hh][Cc][Pp].*'` -ne 0 ]; then
> > > > >
> > > > > ....
> > > > >
> > > > > fi
> > > >
> > > > You do everything you need within sh. Someone else pointed out
> > > > that case/esac is your friend here. It was not quite complete. Here's
> > > > more complete example that will let you pair up the options and their
> > > > arguments if they take them.
> > > >
> > > > ifconfig_args="media 10baseTX dhcp mediaopt half-duplex"
> > > > set -- ${ifconfig_args}
> > > > while [ $# -gt 0 ]; do
> > > > op=$1
> > > > case ${op} in
> > > > [Mm][Ee][Dd][Ii][Aa])
> > > > op_arg=$2
> > > > shift
> > > > echo "op=media op_arg=${op_arg}"
> > > > ;;
> > >
> > > I don't like this. This second-guessing of ifconfig(8)'s arguments
> > > is prone to error - consider the case of a new keyword added to
> > > ifconfig(8).. And blindly discarding unrecognized keyword would
> > > not really work either - a new keyword might take an argument,
> > > the shell script has no way of knowing that, so it would skip
> > > the keyword and try to look at its argument as another keyword;
> > > what if a keyword takes a string argument of, oh, say, 'dhcp'? :)
> >
> > Sorry, but my example was meant to be more featureful than
> > necessary and let you strip it down, sinice you needs wern't completely
> > clear. If you just want to test for a substring, try this instead:
> >
> > case "${ifconfig_args}" in
> > *[Dd][Hh][Cc][Pp]*)
> > echo "we are using dhcp..."
> > ;;
> > esac
> >
> >
> > >
> > > A ${args#dhcp} might work better, but there is a problem with it -
> >
> > The pattern after the # is a regular glob pattern. You can use
> > ${args#[Dd][Hh][Cc][Pp]} to deal with case.
> >
> > You probably really meant to say '${args##*[Dd][Hh][Cc][Pp]*}'
> > which will collapse to a null string if 'dhcp' is in the string, or the
> > string is empty to begin with. With only a single # and no *'s, you will
> > not modify the string unless it is exactly "dhcp".
> >
> > Sill I don't recommend this approach, since you need to test the
> > string twice, once before and once after the expansion. The case/esac
> > idiom is pretty common as well.
>
> I think that the original poster is interested in first testing for
> 'dhcp' in the string, and then removing it - the original post mentioned
> a PR sweep, and I really think he means PR 30441. To correctly process
> an ifconfig_rl0="dhcp media 10baseT/UTP", you'd first have to match
> it against [Dd][Hh][Cc][Pp], and then remove the 'dhcp' part to get
> the real arguments to add to the ifconfig line.
>
> Come to think of it, it might be as easy as: [**UNTESTED**]
>
> case ${ifconfig_args}; in
> [Dd][Hh][Cc][Pp]*)
> set $ifconfig_args
> shift
> ifconfig_add_args="$*"
> ......
>
> ..provided there is a requirement that the ifconfig_args should *start*
> with 'dhcp' (which would be easy enough to meet - right now, the args
> have to *be* 'dhcp', so any additional arguments would be stapled on at
> the end).
This sounds as the best solution. This would allow to set an interface
to be DHCP (variable dhcp_interfaces get set) and take the rest of the
arguments (like media/mediaopt) and apply them to the interface before
the dhclient gets started.
>
> G'luck,
> Peter
>
> --
> If wishes were fishes, the antecedent of this conditional would be true.
>
--
Regards, Ulf.
---------------------------------------------------------------------
Ulf Zimmermann, 1525 Pacific Ave., Alameda, CA-94501, #: 510-865-0204
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