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+.\" 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
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\"     $OpenBSD: strtonum.3,v 1.1 2004/05/03 17:09:24 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 strtol
+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.