|STRTONUM(3)||Library Functions Manual||STRTONUM(3)|
strtonum(const char *nptr,
long long minval, long long
maxval, const char **errstr);
strtonum() function converts the string in nptr to a
long longvalue. The
strtonum() function was designed to facilitate safe, robust programming 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
determined by isspace(3)) followed by a
single optional ‘
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,
stores an error string in *errstr indicating 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
NULLon success; this fact can be used to differentiate a successful return of 0 from an error.
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).
If an error occurs, errstr will be set to one of the following strings:
strtonum() is an OpenBSD extension. The existing alternatives, such as atoi(3) and strtol(3), are either impossible or difficult to use safely.
strtonum() function first appeared in OpenBSD 3.6.
|February 7, 2016||OpenBSD-current|