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.\" Copyright (c) 1990, 1991 The Regents of the University of California.
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.\" All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" Chris Torek and the American National Standards Committee X3,
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.\" on Information Processing Systems.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $OpenBSD: strtoul.3,v 1.21 2013/06/05 03:39:23 tedu Exp $
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.\"
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.Dd $Mdocdate: June 5 2013 $
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.Dt STRTOUL 3
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.Os
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.Sh NAME
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.Nm strtoul ,
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.Nm strtoull ,
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.Nm strtoumax ,
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.Nm strtouq
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.Nd "convert a string to an unsigned long, unsigned long long or uintmax_t integer"
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.Sh SYNOPSIS
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.In limits.h
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.In stdlib.h
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.Ft unsigned long
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.Fn strtoul "const char *nptr" "char **endptr" "int base"
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.Ft unsigned long long
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.Fn strtoull "const char *nptr" "char **endptr" "int base"
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.In inttypes.h
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.Ft uintmax_t
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.Fn strtoumax "const char *nptr" "char **endptr" "int base"
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.In sys/types.h
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.In limits.h
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.In stdlib.h
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.Ft u_quad_t
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.Fn strtouq "const char *nptr" "char **endptr" "int base"
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.Sh DESCRIPTION
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The
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.Fn strtoul
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function converts the string in
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.Fa nptr
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to an
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.Li unsigned long
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value.
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The
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.Fn strtoull
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function converts the string in
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.Fa nptr
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to an
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.Li unsigned long long
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value.
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The
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.Fn strtoumax
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function converts the string in
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.Fa nptr
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to a
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.Li umaxint_t
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value.
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The
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.Fn strtouq
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function is a deprecated equivalent of
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.Fn strtoull
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and is provided for backwards compatibility with legacy programs.
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The conversion is done according to the given
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.Fa base ,
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which must be a number between 2 and 36 inclusive
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or the special value 0.
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If the string in
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.Fa nptr
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represents a negative number, it will be converted to its unsigned equivalent.
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This behavior is consistent with what happens when a signed integer type is
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cast to its unsigned counterpart.
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.Pp
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The string may begin with an arbitrary amount of whitespace
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(as determined by
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.Xr isspace 3 )
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followed by a single optional
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.Ql +
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or
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.Ql -
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sign.
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If
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.Fa base
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is zero or 16, the string may then include a
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.Ql 0x
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prefix, and the number will be read in base 16; otherwise, a zero
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.Fa base
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is taken as 10 (decimal) unless the next character is
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.Ql 0 ,
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in which case it is taken as 8 (octal).
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.Pp
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The remainder of the string is converted to an
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.Li unsigned long
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value in the obvious manner, stopping at the end of the string
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or at the first character that does not produce a valid digit
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in the given base.
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(In bases above 10, the letter
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.Ql A
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in either upper or lower case represents 10,
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.Ql B
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represents 11, and so forth, with
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.Ql Z
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representing 35.)
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.Pp
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If
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.Fa endptr
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is non-null,
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.Fn strtoul
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stores the address of the first invalid character in
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.Fa *endptr .
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If there were no digits at all, however,
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.Fn strtoul
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stores the original value of
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.Fa nptr
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in
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.Fa *endptr .
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(Thus, if
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.Fa *nptr
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is not
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.Ql \e0
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but
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.Fa **endptr
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is
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.Ql \e0
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on return, the entire string was valid.)
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.Sh RETURN VALUES
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The
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.Fn strtoul ,
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.Fn strtoull ,
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.Fn strtoumax
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and
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.Fn strtouq
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functions return either the result of the conversion or,
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if there was a leading minus sign,
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the negation of the result of the conversion,
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unless the original (non-negated) value would overflow.
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If overflow occurs,
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.Fn strtoul
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returns
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.Dv ULONG_MAX ,
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.Fn strtoull
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returns
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.Dv ULLONG_MAX ,
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.Fn strtoumax
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returns
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.Dv UINTMAX_MAX ,
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.Fn strtouq
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returns
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.Dv ULLONG_MAX
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and the global variable
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.Va errno
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is set to
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.Er ERANGE .
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If no conversion could be performed, 0 is returned;
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the global variable
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.Va errno
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is also set to
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.Er EINVAL ,
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though this is not portable across all platforms.
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.Pp
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There is no way to determine if
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.Fn strtoul
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has processed a negative number (and returned an unsigned value) short of
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examining the string in
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.Fa nptr
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directly.
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.Sh EXAMPLES
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Ensuring that a string is a valid number (i.e., in range and containing no
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trailing characters) requires clearing
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.Va errno
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beforehand explicitly since
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.Va errno
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is not changed on a successful call to
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.Fn strtoul ,
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and the return value of
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.Fn strtoul
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cannot be used unambiguously to signal an error:
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.Bd -literal -offset indent
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char *ep;
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unsigned long ulval;
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\&...
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errno = 0;
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ulval = strtoul(buf, &ep, 10);
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if (buf[0] == '\e0' || *ep != '\e0')
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goto not_a_number;
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if (errno == ERANGE && ulval == ULONG_MAX)
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goto out_of_range;
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.Ed
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.Pp
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This example will accept
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.Dq 12
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but not
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.Dq 12foo
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or
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.Dq 12\en .
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If trailing whitespace is acceptable, further checks must be done on
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.Va *ep ;
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alternately, use
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.Xr sscanf 3 .
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.Sh ERRORS
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.Bl -tag -width Er
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.It Bq Er ERANGE
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The given string was out of range; the value converted has been clamped.
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.El
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.Sh SEE ALSO
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.Xr sscanf 3 ,
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.Xr strtol 3
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.Sh STANDARDS
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The
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.Fn strtoul ,
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.Fn strtoull ,
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and
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.Fn strtoumax
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functions conform to
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.St -ansiC-99 .
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The
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.Fn strtouq
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function is a
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.Bx
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extension and is provided for backwards compatibility with legacy programs.
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.Sh BUGS
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Ignores the current locale.
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