NAME

       strtonum — reliably convert string value to an integer

LIBRARY

       Utility functions from BSD systems (libbsd, -lbsd)

SYNOPSIS

       #include <limits.h>
       #include <stdlib.h>
       (See libbsd(7) for include usage.)

       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  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 returned, errno is set, and errstr will point to an error message.
       On success, *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)
                     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

       [EINVAL]           The given string did not consist solely of digit characters; or minval was larger than
                          maxval.

       [ERANGE]           The given string was out of range.

       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),  strtoi(3bsd),  strtol(3),  strtoll(3),
       strtou(3bsd), strtoul(3), strtoull(3)

STANDARDS

       strtonum() is a BSD extension.

HISTORY

       The strtonum() function first appeared in OpenBSD 3.6.   strtonum()  was  redesigned  in  NetBSD  8.0  as
       strtoi(3bsd) and strtou(3bsd).

CAVEATS

       The strtonum() function was designed to facilitate safe, robust programming and overcome the shortcomings
       of the atoi(3) and strtol(3) family of interfaces, however there are problems with the strtonum() API:

       -   will  return  0  on failure; 0 might not be in range, so that necessitates an error check even if you
           want to avoid it

       -   does not differentiate 'illegal' returns, so we can't tell the  difference  between  partial  and  no
           conversions

       -   returns english strings

       -   can't set the base, or find where the conversion ended

       -   hardcodes long long integer type
       To overcome the shortcomings of strtonum() NetBSD provides strtou(3bsd) and strtoi(3bsd).

Debian                                          January 18, 2015                                  strtonum(3bsd)