STRTONUM(3C) Standard C Library Functions STRTONUM(3C)
NAME
strtonum - reliably convert string value to an integer
LIBRARY
Standard C Library (libc, -lc)
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(3C) and
strtol(3C) family of
interfaces.
The string may begin with an arbitrary amount of whitespace (as determined
by
isspace(3C)) 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 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
characters.
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.
INTERFACE STABILITY
Committed.
MT-LEVEL Safe.
SEE ALSO
atof(3C),
atoi(3C),
atol(3C),
atoll(3C),
sscanf(3C),
strtod(3C),
strtol(3C),
strtoul(3C)STANDARDS
strtonum() is an OpenBSD extension. The existing alternatives, such as
atoi(3C) and
strtol(3C), are either impossible or difficult to use safely.
OmniOS February 7, 2016 OmniOS