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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);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       strtof(), strtold():
           _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
           _POSIX_C_SOURCE >= 200112L;
           or cc -std=c99

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.

ERRORS

       ERANGE Overflow or underflow occurred.

CONFORMING TO

       C89 describes strtod(), C99 describes the other two functions.

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.

SEE ALSO

       atof(3), atoi(3), atol(3), strtol(3), strtoul(3)

COLOPHON

       This page is part of release 3.35 of the Linux man-pages project.  A
       description of the project, and information about reporting bugs, can
       be found at http://man7.org/linux/man-pages/.