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38 .\" @(#)strtod.3 5.3 (Berkeley) 6/29/91
40 .\" Modified Sun Aug 21 17:16:22 1994 by Rik Faith (faith@cs.unc.edu)
41 .\" Modified Sat May 04 19:34:31 MET DST 1996 by Michael Haardt
42 .\" (michael@cantor.informatik.rwth-aachen.de)
43 .\" Added strof, strtold, aeb, 2001-06-07
45 .TH STRTOD 3 2014-01-22 "Linux" "Linux Programmer's Manual"
47 strtod, strtof, strtold \- convert ASCII string to floating-point number
49 .B #include <stdlib.h>
51 .BI "double strtod(const char *" nptr ", char **" endptr );
53 .BI "float strtof(const char *" nptr ", char **" endptr );
55 .BI "long double strtold(const char *" nptr ", char **" endptr );
58 Feature Test Macro Requirements for glibc (see
59 .BR feature_test_macros (7)):
66 _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
67 _POSIX_C_SOURCE\ >=\ 200112L;
79 functions convert the initial portion of the string pointed to by
86 representation, respectively.
88 The expected form of the (initial portion of the) string is
89 optional leading white space as recognized by
91 an optional plus (\(aq+\(aq) or minus sign (\(aq\-\(aq) and then either
92 (i) a decimal number, or (ii) a hexadecimal number,
93 or (iii) an infinity, or (iv) a NAN (not-a-number).
97 consists of a nonempty sequence of decimal digits
98 possibly containing a radix character (decimal point, locale-dependent,
99 usually \(aq.\(aq), optionally followed by a decimal exponent.
100 A decimal exponent consists of an \(aqE\(aq or \(aqe\(aq, followed by an
101 optional plus or minus sign, followed by a nonempty sequence of
102 decimal digits, and indicates multiplication by a power of 10.
105 .I "hexadecimal number"
106 consists of a "0x" or "0X" followed by a nonempty sequence of
107 hexadecimal digits possibly containing a radix character,
108 optionally followed by a binary exponent.
110 consists of a \(aqP\(aq or \(aqp\(aq, followed by an optional
111 plus or minus sign, followed by a nonempty sequence of
112 decimal digits, and indicates multiplication by a power of 2.
113 At least one of radix character and binary exponent must be present.
117 is either "INF" or "INFINITY", disregarding case.
121 is "NAN" (disregarding case) optionally followed by \(aq(\(aq,
122 a sequence of characters, followed by \(aq)\(aq.
123 The character string specifies in an implementation-dependent
125 .\" From glibc 2.8's stdlib/strtod_l.c:
126 .\" We expect it to be a number which is put in the
127 .\" mantissa of the number.
129 These functions return the converted value, if any.
134 a pointer to the character after the last character used in the conversion
135 is stored in the location referenced by
138 If no conversion is performed, zero is returned and the value of
140 is stored in the location referenced by
143 If the correct value would cause overflow, plus or minus
147 is returned (according to the sign of the value), and
151 If the correct value would cause underflow, zero is
159 Overflow or underflow occurred.
161 .SS Multithreading (see pthreads(7))
167 functions are thread-safe with exceptions.
168 These functions can be safely used in multithreaded applications,
171 is not called to change the locale during their execution.
176 describes the other two functions.
179 0 can legitimately be returned
180 on both success and failure, the calling program should set
182 to 0 before the call,
183 and then determine if an error occurred by checking whether
185 has a nonzero value after the call.
187 See the example on the
190 the use of the functions described in this manual page is similar.
198 This page is part of release 3.67 of the Linux
201 A description of the project,
202 information about reporting bugs,
203 and the latest version of this page,
205 \%http://www.kernel.org/doc/man\-pages/.