.\" Copyright (c) 1990, 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" Chris Torek and the American National Standards Committee X3,
.\" on Information Processing Systems.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\"
.\"	$OpenBSD: strtonum.3,v 1.2 2004/05/03 17:20:45 tedu Exp $
.\"
.Dd April 29, 2004
.Dt STRTONUM 3
.Os
.Sh NAME
.Nm strtonum
.Nd "reliably convert string value to an integer"
.Sh SYNOPSIS
.Fd #include <stdlib.h>
.Fd #include <limits.h>
.Ft unsigned long long
.Fo strtonum
.Fa "const char *nptr"
.Fa "long long minval"
.Fa "unsigned long long maxval"
.Fa "const char **errstr"
.Fc
.Sh DESCRIPTION
The
.Fn strtonum
function converts the string in
.Fa nptr
to an
.Li unsigned long long
value.
The conversion is done according to base 10.
Negative values may be obtained by casting the result.
.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 an
.Li unsigned long long
value in the obvious manner,
stopping at the first character which is not a valid digit
in the given base.
.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 *endptr
indicating the failure.
.Sh RETURN VALUES
The
.Fn strtonum
function returns the result of the conversion,
unless the value would underflow or overflow.
On error, 0 is returned.
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er ERANGE
The given string was out of range.
.It Bq Er EINVAL
The given string did not consist solely of a valid number.
.El
.Sh SEE ALSO
.Xr atof 3 ,
.Xr atoi 3 ,
.Xr atol 3 ,
.Xr atoll 3 ,
.Xr sscanf 3 ,
.Xr strtol 3 ,
.Xr strtod 3 ,
.Xr strtoul 3
.Sh STANDARDS
.Fn strtonum
is an
.Ox
extension.