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STRTONUM(3)	       FreeBSD Library Functions Manual		   STRTONUM(3)

NAME
     strtonum -- reliably convert string value to an integer

SYNOPSIS
     #include <stdlib.h>
     #include <limits.h>

     long long
     strtonum(const char *nptr,	long long minval, long long maxval,
	 const char **errstr);

DESCRIPTION
     The strtonum() function converts the string in nptr to a long long	value.
     The strtonum() function was designed to facilitate	safe, robust program-
     ming and overcome the shortcomings	of the atoi(3) and strtol(3) family of
     interfaces.

     The string	may begin with an arbitrary amount of whitespace (as deter-
     mined by isspace(3)) followed by a	single optional	`+' or `-' sign.

     The remainder of the string is converted to a long	long value according
     to	base 10.

     The value obtained	is then	checked	against	the provided minval and	maxval
     bounds.  If errstr	is non-null, strtonum()	stores an error	string in
     *errstr indicating	the failure.

RETURN VALUES
     The strtonum() function returns the result	of the conversion, unless the
     value would exceed	the provided bounds or is invalid.  On error, 0	is
     returned, errno is	set, and errstr	will point to an error message.
     *errstr will be set to NULL on success; this fact can be used to differ-
     entiate a successful return of 0 from an error.

EXAMPLES
     Using strtonum() correctly	is meant to be simpler than the	alternative
     functions.

	   int iterations;
	   const char *errstr;

	   iterations =	strtonum(optarg, 1, 64,	&errstr);
	   if (errstr)
		   errx(1, "number of iterations is %s:	%s", errstr, optarg);

     The above example will guarantee that the value of	iterations is between
     1 and 64 (inclusive).

ERRORS
     [ERANGE]		The given string was out of range.

     [EINVAL]		The given string did not consist solely	of digit char-
			acters.

     [EINVAL]		minval was larger than maxval.

     If	an error occurs, errstr	will be	set to one of the following strings:

     too large	  The result was larger	than the provided maximum value.
     too small	  The result was smaller than the provided minimum value.
     invalid	  The string did not consist solely of digit characters.

SEE ALSO
     atof(3), atoi(3), atol(3),	atoll(3), sscanf(3), strtod(3),	strtol(3),
     strtoul(3)

STANDARDS
     strtonum()	is a BSD extension.  The existing alternatives,	such as
     atoi(3) and strtol(3), are	either impossible or difficult to use safely.

HISTORY
     The strtonum() function first appeared in OpenBSD 3.6.

FreeBSD	10.1			April 29, 2004			  FreeBSD 10.1

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | EXAMPLES | ERRORS | SEE ALSO | STANDARDS | HISTORY

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