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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;   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

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       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.