strtod(3) - Linux manual page (original) (raw)
strtod(3) Library Functions Manual strtod(3)
NAME top
strtod, strtof, strtold - convert ASCII string to floating-point
numberLIBRARY top
Standard C library (_libc_, _-lc_)SYNOPSIS top
**#include <stdlib.h>**
**double strtod(const char *restrict** _nptr_**,**
**char _Nullable restrict** _endptr_**);**
**float strtof(const char *restrict** _nptr_**,**
**char _Nullable restrict** _endptr_**);**
**long double strtold(const char *restrict** _nptr_**,**
**char _Nullable restrict** _endptr_**);**Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
**strtof**(), **strtold**():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112LDESCRIPTION top
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)](../man3/isspace.3.html), 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
string, _(n-char-sequence)_, where _n-char-sequence_ specifies in an
implementation-dependent way the type of NAN (see VERSIONS).RETURN VALUE top
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 (unless _endptr_
is null) 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**, or **HUGE_VALL** is returned (according to the return type
and sign of the value), and **ERANGE** is stored in _[errno](../man3/errno.3.html)_.
If the correct value would cause underflow, a value with magnitude
no larger than **DBL_MIN**, **FLT_MIN**, or **LDBL_MIN** is returned and
**ERANGE** is stored in _[errno](../man3/errno.3.html)_.ERRORS top
**ERANGE** Overflow or underflow occurred.ATTRIBUTES top
For an explanation of the terms used in this section, see
[attributes(7)](../man7/attributes.7.html).
┌───────────────────────────────┬───────────────┬────────────────┐
│ **Interface** │ **Attribute** │ **Value** │
├───────────────────────────────┼───────────────┼────────────────┤
│ **strtod**(), **strtof**(), **strtold**() │ Thread safety │ MT-Safe locale │
└───────────────────────────────┴───────────────┴────────────────┘VERSIONS top
In the glibc implementation, the _n-char-sequence_ that optionally
follows "NAN" is interpreted as an integer number (with an
optional '0' or '0x' prefix to select base 8 or 16) that is to be
placed in the mantissa component of the returned value.STANDARDS top
C11, POSIX.1-2008.HISTORY top
**strtod**()
C89, POSIX.1-2001.
**strtof**()
**strtold**()
C99, POSIX.1-2001.CAVEATS top
Since 0 can legitimately be returned on both success and failure,
the calling program should set _[errno](../man3/errno.3.html)_ to 0 before the call, and
then determine if an error occurred by checking whether _[errno](../man3/errno.3.html)_ has
a nonzero value after the call.EXAMPLES top
See the example on the [strtol(3)](../man3/strtol.3.html) manual page; the use of the
functions described in this manual page is similar.SEE ALSO top
[atof(3)](../man3/atof.3.html), [atoi(3)](../man3/atoi.3.html), [atol(3)](../man3/atol.3.html), [nan(3)](../man3/nan.3.html), [nanf(3)](../man3/nanf.3.html), [nanl(3)](../man3/nanl.3.html), [strfromd(3)](../man3/strfromd.3.html),
[strtol(3)](../man3/strtol.3.html), [strtoul(3)](../man3/strtoul.3.html)COLOPHON top
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man-pages@man7.orgLinux man-pages 6.10 2024-07-23 strtod(3)
Pages that refer to this page:gawk(1), pcpintro(1), pmstore(1), strace(1), atof(3), atoi(3), nan(3), sscanf(3), strfromd(3), strtol(3), strtoul(3), locale(7)