Name
strtod, strtof, strtold — convert ASCII string to floating point number
Synopsis
#include <stdlib.h>
double strtod( |
const char * | nptr, |
| char ** | endptr); |
float
strtof( |
const char * | nptr, |
| char ** | endptr); |
long
double strtold( |
const char * | nptr, |
| char ** | endptr); |
![[Note]](../stylesheet/note.png) |
Note | |||
|---|---|---|---|---|
|
DESCRIPTION
The strtod(), strtof(), and strtold() functions convert the initial
portion of the string pointed to by nptr to double, float, and
long double representation,
respectively.
The expected form of the (initial portion of the) string is optional leading white space as recognized by isspace(3), an optional plus ('+') or minus sign ('−') and then either (i) a decimal number, or (ii) a hexadecimal number, or (iii) an infinity, or (iv) a NAN (not-a-number).
A decimal number consists of a nonempty sequence of decimal digits possibly containing a radix character (decimal point, locale-dependent, usually '.'), optionally followed by a decimal exponent. A decimal exponent consists of an 'E' or 'e', followed by an optional plus or minus sign, followed by a nonempty sequence of decimal digits, and indicates multiplication by a power of 10.
A hexadecimal number consists of a "0x" or "0X" followed by a nonempty sequence of hexadecimal digits possibly containing a radix character, optionally followed by a binary exponent. A binary exponent consists of a 'P' or 'p', followed by an optional plus or minus sign, followed by a nonempty sequence of decimal digits, and indicates multiplication by a power of 2. At least one of radix character and binary exponent must be present.
An “infinity” is either "INF" or "INFINITY", disregarding case.
A NAN is "NAN" (disregarding
case) optionally followed by '(', a sequence of characters,
followed by ')'. The character string specifies in an
implementation-dependent way the type of NAN.
RETURN VALUE
These functions return the converted value, if any.
If endptr is not
NULL, a pointer to the character after the last character
used in the conversion is stored in the location referenced
by endptr.
If no conversion is performed, zero is returned and the
value of nptr is
stored in the location referenced by endptr.
If the correct value would cause overflow, plus or minus
HUGE_VAL (HUGE_VALF, HUGE_VALL) is returned (according to the
sign of the value), and ERANGE
is stored in errno. If the
correct value would cause underflow, zero is returned and
ERANGE is stored in
errno.
NOTES
Since 0 can legitimately be returned on both success and
failure, the calling program should set errno to 0 before the call, and then
determine if an error occurred by checking whether
errno has a nonzero value after
the call.
EXAMPLE
See the example on the strtol(3) manual page; the use of the functions described in this manual page is similar.
COLOPHON
This page is part of release 2.79 of the Linux man-pages project. A
description of the project, and information about reporting
bugs, can be found at
http://www.kernel.org/doc/man-pages/.
|
Copyright (c) 1990, 1991 The Regents of the University of California. All rights reserved. This code is derived from software contributed to Berkeley by 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. All advertising materials mentioning features or use of this software must display the following acknowledgement: This product includes software developed by the University of California, Berkeley and its contributors. 4. 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. (#)strtod.3 5.3 (Berkeley) 6/29/91 Modified Sun Aug 21 17:16:22 1994 by Rik Faith (faithcs.unc.edu) Modified Sat May 04 19:34:31 MET DST 1996 by Michael Haardt (michaelcantor.informatik.rwth-aachen.de) Added strof, strtold, aeb, 2001-06-07 |