STRTONUM(3C) Standard C Library Functions STRTONUM(3C)
- reliably convert string value to an integer
Standard C Library (libc, -lc)
SYNOPSIS #include <stdlib.h> long long strtonum
(const char *nptr
, long long minval
, long long maxval
, const char **errstr
() function converts the string in nptr
to a long long value.
() function was designed to facilitate safe, robust programming
and overcome the shortcomings of the atoi(3C)
The string may begin with an arbitrary amount of whitespace (as determined
) followed by a single optional `+' or `-' sign.
The remainder of the string is converted to a long long value according to
The value obtained is then checked against the provided minval
bounds. If errstr
is non-null, strtonum
() stores an error string in errstr
indicating the failure.
() function returns the result of the conversion, unless the
value would exceed the provided bounds or is invalid. On error, 0 is
is set, and errstr
will point to an error message. errstr
will be set to NULL on success; this fact can be used to differentiate a
successful return of 0 from an error.
() correctly is meant to be simpler than the alternative
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).
ERANGE The given string was out of range.
EINVAL The given string did not consist solely of digit
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.
INTERFACE STABILITY Committed
SEE ALSO atof(3C)
() is an OpenBSD extension. The existing alternatives, such as atoi(3C)
, are either impossible or difficult to use safely.
OmniOS February 7, 2016 OmniOS