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From: meissner@skeptic.osf.org (Michael Meissner)
Newsgroups: comp.lang.c
Subject: Re: Is There A Way To Check If argv[1] Is An Integer?
Message-ID: <2232@paperboy.OSF.ORG>
Date: 22 Dec 89 16:33:18 GMT
References: <984@ux.acss.umn.edu> <11467@csli.Stanford.EDU> <636@chem.ucsd.EDU>
Sender: news@OSF.ORG
Reply-To: meissner@skeptic.osf.org (Michael Meissner)
Organization: Open Software Foundation
Lines: 32

In article <636@chem.ucsd.EDU> tps@chem.ucsd.edu (Tom Stockfisch) writes:

	(deleted text asking for a way to determine if argv[x] is a
	number)

>How about
>
>int	/* really BOOL */
>isInteger(string)
>	char	*string;
>{
>	char	*endptr;
>
>	(void)strtol( string, &endptr, 10 );
>	return	endptr != string;
>}

You really should check to see if there is any trailing non-digits, as
well as properly declaring strtol.  Also, you should consider whether
to require the number to be decimal only, or that it can be written in
C notation (decimal, octal, or hex -- I prefer allowing all three):

int	/* really BOOL */
isInteger(string)
	char *string;
{
	extern long strtol();
	char *endptr;

	(void) strtol (string, &endptr, 0);
	return (endptr != string) && (*endptr == '\0');
}