mirror of https://github.com/mkerrisk/man-pages
173 lines
5.6 KiB
Groff
173 lines
5.6 KiB
Groff
.\" 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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.\" the American National Standards Committee X3, on Information
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.\" 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. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. 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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.\" @(#)strtod.3 5.3 (Berkeley) 6/29/91
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.\"
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.\" Modified Sun Aug 21 17:16:22 1994 by Rik Faith (faith@cs.unc.edu)
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.\" Modified Sat May 04 19:34:31 MET DST 1996 by Michael Haardt
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.\" (michael@cantor.informatik.rwth-aachen.de)
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.\" Added strof, strtold, aeb, 2001-06-07
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.\"
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.TH STRTOD 3 2007-07-26 "Linux" "Linux Programmer's Manual"
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.SH NAME
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strtod, strtof, strtold \- convert ASCII string to floating point number
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.SH SYNOPSIS
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.B #include <stdlib.h>
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.sp
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.BI "double strtod(const char *" nptr ", char **" endptr );
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.br
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.BI "float strtof(const char *" nptr ", char **" endptr );
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.br
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.BI "long double strtold(const char *" nptr ", char **" endptr );
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.sp
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.in -4n
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Feature Test Macro Requirements for glibc (see
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.BR feature_test_macros (7)):
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.in
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.sp
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.BR strtof (),
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.BR strtold ():
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_XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE; or
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.I cc\ -std=c99
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.SH DESCRIPTION
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The
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.BR strtod (),
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.BR strtof (),
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and
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.BR strtold ()
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functions convert the initial portion of the string pointed to by
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.I nptr
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to
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.IR double ,
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.IR float ,
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and
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.I long double
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representation, respectively.
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The expected form of the (initial portion of the) string is
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optional leading white space as recognized by
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.BR isspace (3),
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an optional plus (\(aq+\(aq) or minus sign (\(aq\-\(aq) and then either
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(i) a decimal number, or (ii) a hexadecimal number,
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or (iii) an infinity, or (iv) a NAN (not-a-number).
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.LP
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A
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.I "decimal number"
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consists of a non-empty sequence of decimal digits
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possibly containing a radix character (decimal point, locale-dependent,
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usually \(aq.\(aq), optionally followed by a decimal exponent.
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A decimal exponent consists of an \(aqE\(aq or \(aqe\(aq, followed by an
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optional plus or minus sign, followed by a non-empty sequence of
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decimal digits, and indicates multiplication by a power of 10.
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.LP
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A
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.I "hexadecimal number"
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consists of a "0x" or "0X" followed by a non-empty sequence of
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hexadecimal digits possibly containing a radix character,
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optionally followed by a binary exponent.
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A binary exponent
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consists of a \(aqP\(aq or \(aqp\(aq, followed by an optional
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plus or minus sign, followed by a non-empty sequence of
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decimal digits, and indicates multiplication by a power of 2.
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At least one of radix character and binary exponent must be present.
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.LP
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An
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.I infinity
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is either "INF" or "INFINITY", disregarding case.
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.LP
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A
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.I NAN
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is "NAN" (disregarding case) optionally followed by \(aq(\(aq,
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a sequence of characters, followed by \(aq)\(aq.
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The character string specifies in an implementation-dependent
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way the type of NAN.
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.SH "RETURN VALUE"
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These functions return the converted value, if any.
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If
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.I endptr
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is not NULL,
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a pointer to the character after the last character used in the conversion
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is stored in the location referenced by
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.IR endptr .
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If no conversion is performed, zero is returned and the value of
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.I nptr
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is stored in the location referenced by
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.IR endptr .
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If the correct value would cause overflow, plus or minus
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.B HUGE_VAL
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.RB ( HUGE_VALF ,
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.BR HUGE_VALL )
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is returned (according to the sign of the value), and
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.B ERANGE
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is stored in
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.IR errno .
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If the correct value would cause underflow, zero is
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returned and
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.B ERANGE
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is stored in
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.IR errno .
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.SH ERRORS
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.TP
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.B ERANGE
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Overflow or underflow occurred.
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.SH "CONFORMING TO"
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C89 describes
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.BR strtod (),
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C99
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describes the other two functions.
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.SH NOTES
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Since
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0 can legitimately be returned
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on both success and failure, the calling program should set
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.I errno
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to 0 before the call,
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and then determine if an error occurred by checking whether
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.I errno
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has a non-zero value after the call.
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.SH EXAMPLE
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See the example on the
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.BR strtol (3)
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manual page;
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the use of the functions described in this manual page is similar.
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.SH "SEE ALSO"
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.BR atof (3),
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.BR atoi (3),
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.BR atol (3),
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.BR strtol (3),
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.BR strtoul (3)
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