STRTOD(3)                                           Linux Programmer's Manual                                          STRTOD(3)



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; 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  multiplica-
       tion 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 loca-
       tion 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 3.25 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/.



Linux                                                      2007-07-26                                                  STRTOD(3)