Section (3) strtod
strtod, strtof, strtold — convert ASCII string to floating-point number
||const char *nptr,|
||const char *nptr,|
||const char *nptr,|
strtold() functions convert the initial
portion of the string pointed to by
nptr to double, float, and
long double representation,
The expected form of the (initial portion of the) string is optional leading white space as recognized by isspace(3), an optional plus (_zsingle_quotesz_+_zsingle_quotesz_) or minus sign (_zsingle_quotesz_−_zsingle_quotesz_) 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 _zsingle_quotesz_._zsingle_quotesz_), optionally followed by a decimal exponent. A decimal exponent consists of an _zsingle_quotesz_E_zsingle_quotesz_ or _zsingle_quotesz_e_zsingle_quotesz_, 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 _zsingle_quotesz_P_zsingle_quotesz_ or _zsingle_quotesz_p_zsingle_quotesz_, 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.
NAN is NAN (disregarding
case) optionally followed by a string,
specifies in an implementation-dependent way the type of NAN
These functions return the converted value, if any.
endptr is not
NULL, a pointer to the character after the last character
used in the conversion is stored in the location referenced
If no conversion is performed, zero is returned and
null) the value of
nptr is stored in the location
If the correct value would cause overflow, plus or minus
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
For an explanation of the terms used in this section, see attributes(7).
||Thread safety||MT-Safe locale|
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
In the glibc implementation, the
optionally follows NAN is interpreted as an integer number
(with an optional _zsingle_quotesz_0_zsingle_quotesz_ or _zsingle_quotesz_0x_zsingle_quotesz_ prefix to select base 8 or 16)
that is to be placed in the mantissa component of the
See the example on the strtol(3) manual page; the use of the functions described in this manual page is similar.
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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
the American National Standards Committee X3, on Information
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
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
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3. All advertising materials mentioning features or use of this software
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This product includes software developed by the University of
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THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS_zsingle_quotesz__zsingle_quotesz_ AND
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(#)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
Added strof, strtold, aeb, 2001-06-07