Date: Mon, 10 Aug 2020 16:44:53 +0200 From: Polytropon <freebsd@edvax.de> To: Ernie Luzar <luzar722@gmail.com> Cc: "freebsd-questions@freebsd.org" <freebsd-questions@freebsd.org> Subject: Re: csh use of grep | tr commands Message-ID: <20200810164453.378835aa.freebsd@edvax.de> In-Reply-To: <5F30962B.5060005@gmail.com> References: <5F30962B.5060005@gmail.com>
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On Sun, 09 Aug 2020 20:34:51 -0400, Ernie Luzar wrote:
> Double quotes are giving me trouble.
>
> I have a file with a line in it like this
> ip4="10.111.098.2"
> I want to get just the ip address
>
> ip=`grep "ip4=" directory-path/file-name
>
> $ip ends up having ip4="10.111.098.2" in it
>
> ip=`echo -n "${ip}" | tr -d "ip4="
>
> $ip ends up having "10.111.098.2" in it
>
> Putting | tr """ " "` after the echo above gives error.
>
> How do I remove the " around the ip address?
Without any insult: You're using the wrong tool.
While the C shell is acceptable as an interactive shell
(and I even prefer it over bash to a certain degree),
it's absolutely terrible, and I may even say unsuited
for scripting.
The system's default scripting shell is sh. Use that.
See "man sh" for quoting rules. It makes your life
easier and more portable. :-)
You can use bash to interactively develop sh scripts;
even for creating one-liners bash is very convenient.
Back on topic. If you don't mind an additional program
call to sed, you can use the "replace with nothing"
method:
% echo 'those "are" quotes' | sed 's/"//g'
those are quotes
This example is from a C shell session. :-)
Applied to your initial problem:
% echo 'ip4="10.111.098.2"' | sed 's/ip4="//g; s/"//g'
10.111.098.2
You can use sed for multiple "replace with nothing"
statements.
Allow me to leave a pointer to the following article:
Tom Christiansen:
Csh Programming Considered Harmful
http://harmful.cat-v.org/software/csh
If you want to process some input files and do something
with the lines they contain, use the right tool: This is
often perl, but can also be sh or bash. It cannot be csh.
That's the truth. ;-)
I'd like to remind all readers that I've written one
(in numbers: 1) script in the C shell which still works
and which I still use from time to time. But I cannot
recommend following my example, and I have promised
to never do it again. :-)
--
Polytropon
Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...
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