Skip site navigation (1)Skip section navigation (2)
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>

next in thread | previous in thread | raw e-mail | index | archive | help
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



Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20050515133928.F10135>