295 lines
6.5 KiB
Groff
295 lines
6.5 KiB
Groff
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.\" $NetBSD: strtol.3,v 1.26 2009/07/23 13:38:57 wiz Exp $
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.\"
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.\" Copyright (c) 1990, 1991, 1993
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.\" The Regents of the University of California. 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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.\" from: @(#)strtol.3 8.1 (Berkeley) 6/4/93
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.\"
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.Dd July 23, 2009
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.Dt STRTOL 3
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.Os
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.Sh NAME
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.Nm strtol ,
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.Nm strtoll ,
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.Nm strtoimax ,
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.Nm strtoq
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.Nd convert string value to a long, long long, intmax_t or quad_t integer
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In stdlib.h
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.In limits.h
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.Ft long int
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.Fn strtol "const char * restrict nptr" "char ** restrict endptr" "int base"
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.Ft long long int
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.Fn strtoll "const char * restrict nptr" "char ** restrict endptr" "int base"
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.Pp
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.In inttypes.h
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.Ft intmax_t
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.Fn strtoimax "const char * restrict nptr" "char ** restrict endptr" "int base"
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.Pp
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.In sys/types.h
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.In stdlib.h
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.In limits.h
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.Ft quad_t
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.Fn strtoq "const char * restrict nptr" "char ** restrict endptr" "int base"
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.Sh DESCRIPTION
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The
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.Fn strtol
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function
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converts the string in
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.Fa nptr
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to a
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.Ft long int
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value.
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The
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.Fn strtoll
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function
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converts the string in
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.Fa nptr
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to a
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.Ft long long int
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value.
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The
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.Fn strtoimax
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function
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converts the string in
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.Fa nptr
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to an
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.Ft intmax_t
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value.
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The
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.Fn strtoq
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function
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converts the string in
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.Fa nptr
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to a
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.Ft quad_t
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value.
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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 between 2 and 36 inclusive,
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or be the special value 0.
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.Pp
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The string may begin with an arbitrary amount of white space
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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,
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the string may then include a
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.Ql 0x
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prefix,
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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 a
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.Em long
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value in the obvious manner,
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stopping at the first character which is not 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
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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-nil,
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.Fn strtol
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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 strtol
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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 strtol
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function
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returns the result of the conversion,
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unless the value would underflow or overflow.
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If an underflow occurs,
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.Fn strtol
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returns
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.Dv LONG_MIN ,
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.Fn strtoll
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returns
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.Dv LLONG_MIN ,
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and
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.Fn strtoimax
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returns
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.Dv INTMAX_MIN .
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If an overflow occurs,
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.Fn strtol
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returns
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.Dv LONG_MAX ,
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.Fn strtoll
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returns
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.Dv LLONG_MAX ,
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and
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.Fn strtoimax
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returns
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.Dv INTMAX_MAX .
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In these cases,
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.Va errno
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is set to
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.Er ERANGE .
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If the
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.Fa base
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argument is not supported then
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.Va errno
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is set to
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.Er EINVAL
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and the functions return 0.
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.Pp
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If no error occurs,
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.Va errno
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is left unchanged.
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This behavior (which is unlike most library functions) is guaranteed
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by the pertinent standards.
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.Sh EXAMPLES
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Because the return value of
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.Fn strtol
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cannot be used unambiguously to detect an error,
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.Va errno
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is left unchanged after a successful call.
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To ensure that a string is a valid number (i.e., in range and containing no
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trailing characters), clear
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.Va errno
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beforehand explicitly, then check it afterwards:
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.Bd -literal -offset indent
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char *ep;
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long lval;
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\&...
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errno = 0;
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lval = strtol(buf, \*[Am]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 \*[Am]\*[Am] (lval == LONG_MAX || lval == LONG_MIN))
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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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.Pp
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If
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.Fn strtol
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is being used instead of
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.Xr atoi 3 ,
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error checking is further complicated because the desired return value is an
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.Li int
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rather than a
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.Li long ;
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however, on some architectures integers and long integers are the same size.
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Thus the following is necessary:
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.Bd -literal -offset indent
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char *ep;
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int ival;
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long lval;
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\&...
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errno = 0;
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lval = strtol(buf, \*[Am]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 \*[Am]\*[Am] (lval == LONG_MAX || lval == LONG_MIN)) ||
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(lval \*[Gt] INT_MAX || lval \*[Lt] INT_MIN))
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goto out_of_range;
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ival = lval;
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.Ed
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.Sh ERRORS
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The
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.Ar base
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is not between 2 and 36 and does not contain the special value 0.
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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 atof 3 ,
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.Xr atoi 3 ,
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.Xr atol 3 ,
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.Xr atoll 3 ,
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.Xr strtod 3 ,
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.Xr strtoul 3 ,
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.Xr strtoull 3 ,
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.Xr strtoumax 3
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.Sh STANDARDS
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The
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.Fn strtol
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function
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conforms to
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.St -ansiC .
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The
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.Fn strtoll
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and
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.Fn strtoimax
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functions conform to
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.St -isoC-99 .
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.Sh BUGS
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Ignores the current locale.
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