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Date: Sun, 15 May 2005 13:44:20 -0700 (PDT)
From: =?ISO-8859-1?Q?Mikko_Ty=F6l=E4j=E4rvi?= <mbsd@pacbell.net>
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To: Ian Smith <smithi@nimnet.asn.au>
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cc: freebsd-questions@freebsd.org
Subject: Re: simple? sh problen
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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