STRTONUM
Section: Misc. Reference Manual Pages (3bsd)
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BSD mandoc
NAME
strtonum
- reliably convert string value to an integer
LIBRARY
Lb libbsd
SYNOPSIS
In limits.h
In stdlib.h
(See
libbsd(7)
for include usage.)
Ft long long
Fo strtonum
Fa const char *nptr
Fa long long minval
Fa long long maxval
Fa const char **errstr
Fc
DESCRIPTION
The
Fn strtonum
function converts the string in
Fa nptr
to a
Vt 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
Vt long long
value according to base 10.
The value obtained is then checked against the provided
Fa minval
and
Fa maxval
bounds.
If
Fa errstr
is non-null,
Fn strtonum
stores an error string in
Fa *errstr
indicating the failure.
RETURN VALUES
The
Fn 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
Fa errstr
will point to an error message.
On success,
Fa *errstr
will be set to
NULL
this fact can be used to differentiate
a successful return of 0 from an error.
EXAMPLES
Using
Fn 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
- Bq Er EINVAL
-
The given string did not consist solely of digit characters; or
minval
was larger than
maxval
- Bq Er ERANGE
-
The given string was out of range.
If an error occurs,
Fa 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
Fn strtonum
is an
Ox extension.
HISTORY
The
Fn strtonum
function first appeared in
Ox 3.6 .
Fn strtonum
was redesigned in
Nx 8
as
Fn strtoi 3bsd
and
Fn strtou 3bsd .
CAVEATS
The
Fn 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
Fn 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
Fn strtonum
Nx provides
Fn strtou 3bsd
and
Fn strtoi 3bsd .