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STRTONUM(3)		     Library Functions Manual		     STRTONUM(3)

NAME
     strtonum -- reliably convert string value to an integer

SYNOPSIS
     #include <stdlib.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 programming
     and overcome the shortcomings of the atoi(3) and strtol(3) family of inter-
     faces.

     The string may begin with an arbitrary amount of whitespace (as  determined
     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 re-
     turned, errno is set, and errstr will point to an error message.	On  suc-
     cess, *errstr will be set to NULL; this fact can be used to differentiate 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 != NULL)
		   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 charac-
			ters.

     [EINVAL]		The supplied 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), str-
     toul(3)

STANDARDS
     The strtonum() function 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 15.1			 April 29, 2004 		     STRTONUM(3)
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