Date: Thu, 24 Jun 2010 12:31:13 +0200 From: Thomas <fwd@gothschlampen.com> To: Aiza <aiza21@comclark.com> Cc: questions@freebsd.org Subject: Re: .sh check for numeric content Message-ID: <20100624103113.GA27123@gothschlampen.com> In-Reply-To: <4C22E4A0.1040206@comclark.com> References: <4C22B3D7.6070102@comclark.com> <20100624013755.GA5009@gothschlampen.com> <4C22C816.3000105@comclark.com> <4C22E4A0.1040206@comclark.com>
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On Thu, Jun 24, 2010 at 12:52:48PM +0800, Aiza wrote:
Hello,
> But when I tried this format
> [ expr "${dup_times}" : "[0-9]*$" ] || echo "value is not numeric"
>
> I get the error message no mater what the value is.
>
> What am I doing wrong?
Even if "[" at first glance seems like a special syntax of the shell,
it really is just an alternative name or way of calling test(1):
$ ls -l $(which test [)
-rwxr-xr-x 1 root root 42584 2009-10-06 13:07 /usr/bin/[
-rwxr-xr-x 1 root root 30284 2009-10-06 13:07 /usr/bin/test
(this actually is from a Linux system)
You can read about the checks test(1) can perform and its syntax in its
manual page. It will give you a nice and concise overview of what can be
archived in this "[ $EXPRESSION ]" syntax, and what checks are left to
be performed in other ways. Hope this helps.
Regards,
Thomas
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