Date: Sun, 15 May 2005 13:44:20 -0700 (PDT) From: =?ISO-8859-1?Q?Mikko_Ty=F6l=E4j=E4rvi?= <mbsd@pacbell.net> To: Ian Smith <smithi@nimnet.asn.au> Cc: freebsd-questions@freebsd.org Subject: Re: simple? sh problen Message-ID: <20050515133928.F10135@sotec.home> In-Reply-To: <Pine.BSF.3.96.1050516041643.18128B-100000@gaia.nimnet.asn.au> References: <Pine.BSF.3.96.1050516041643.18128B-100000@gaia.nimnet.asn.au>
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On Mon, 16 May 2005, Ian Smith wrote:
> Hopefully not too OT .. the only silly question being the unasked one ..
>
> How do I test whether a sh argument is an integer or not, so as to avoid
> failing on a syntax error from otherwise working code such as:
>
> [ $3 -lt 10 -o $3 -gt 600 ] && echo "$0 $1 $2: $3 invalid" && exit 1
>
> when $3 is a non-integer argument? Do I need to delve into awk and REs,
> or is there something more simple I've missed in mans test, expr, etc?
Here are some suggestions for functions to do the test:
isnum() {
expr "$1" : '^[0-9][0-9]*$' >/dev/null
}
isnum() {
case "$1" in
*[^0-9]*|'') return 1;;
esac
return 0
}
The second one is likely to be faster unless "expr" is a shell builtin
(typically it it not).
$.02,
/Mikko
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