\" $NetBSD: strtonum.3,v 1.2 2015/01/19 11:47:41 wiz Exp $
\" $OpenBSD: strtonum.3,v 1.17 2013/08/14 06:32:28 jmc Exp $
\"
\" Copyright (c) 2004 Ted Unangst
\"
\" Permission to use, copy, modify, and distribute this software for any
\" purpose with or without fee is hereby granted, provided that the above
\" copyright notice and this permission notice appear in all copies.
\"
\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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\"
Dd January 18, 2015
Dt STRTONUM 3
Os
Sh NAME
Nm strtonum
Nd reliably convert string value to an integer
Sh SYNOPSIS
Vt #define _OPENBSD_SOURCE
In stdlib.h
Ft long long
Fo strtonum
Fa "const char *nptr"
Fa "long long minval"
Fa "long long maxval"
Fa "const char **errstr"
Fc
Sh DESCRIPTION
The
Fn strtonum
function converts the string in
Fa nptr
to a
Li long long
value.
Pp
The string may begin with an arbitrary amount of whitespace
(as determined by
Xr isspace 3 )
followed by a single optional
Ql +
or
Ql -
sign.
Pp
The remainder of the string is converted to a
Li long long
value according to base 10.
Pp
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.
Sh 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,
Va errno
is set, and
Fa errstr
will point to an error message.
Fa *errstr
will be set to
Dv NULL
on success;
this fact can be used to differentiate
a successful return of 0 from an error.
Sh EXAMPLES
Using
Fn strtonum
correctly is meant to be simpler than the alternative functions.
Bd -literal -offset indent
int iterations;
const char *errstr;
iterations = strtonum(optarg, 1, 64, &errstr);
if (errstr)
errx(1, "number of iterations is %s: %s", errstr, optarg);
Ed
Pp
The above example will guarantee that the value of iterations is between
1 and 64 (inclusive).
Sh ERRORS
Bl -tag -width Er
It Bq Er EINVAL
The given string did not consist solely of digit characters; or
Ar minval
was larger than
Ar maxval .
It Bq Er ERANGE
The given string was out of range.
El
Pp
If an error occurs,
Fa errstr
will be set to one of the following strings:
Pp
Bl -tag -width "too largeXX" -compact
It Qq too large
The result was larger than the provided maximum value.
It Qq too small
The result was smaller than the provided minimum value.
It Qq invalid
The string did not consist solely of digit characters.
El
Sh SEE ALSO
Xr atof 3 ,
Xr atoi 3 ,
Xr atol 3 ,
Xr atoll 3 ,
Xr sscanf 3 ,
Xr strtod 3 ,
Xr strtoi 3 ,
Xr strtol 3 ,
Xr strtoll 3 ,
Xr strtou 3 ,
Xr strtoul 3 ,
Xr strtoull 3
Sh STANDARDS
Fn strtonum
is an
Ox
extension.
Sh HISTORY
The
Fn strtonum
function first appeared in
Ox 3.6 .
Fn strtonum
was redesigned in
Nx 8
as
Fn strtoi 3
and
Fn strtou 3 .
For compatibility reasons it's available since
Nx 8
in the
Vt _OPENBSD_SOURCE
namespace.
Sh CAVEATS
The
Fn strtonum
function was designed to facilitate safe,
robust programming and overcome the shortcomings of the
Xr atoi 3
and
Xr strtol 3
family of interfaces, however there are problems with the
Fn strtonum
API:
Bl -dash
It
will return 0 on failure; 0 might not be in range, so that necessitates
an error check even if you want to avoid it
It
does not differentiate 'illegal' returns, so we can't tell the
difference between partial and no conversions
It
returns english strings
It
can't set the base, or find where the conversion ended
It
hardcodes long long integer type
El
To overcome the shortcomings of
Fn strtonum
Nx
provides
Fn strtou 3
and
Fn strtoi 3 .
