STRTOD(3)



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 ||
           _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 pos-
       sibly 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 NOTES).

RETURN VALUE
       These functions return the converted value, if any.

       If endptr is not NULL, a pointer to the character after the last  char-
       acter  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.

ATTRIBUTES
   Multithreading (see pthreads(7))
       The strtod(), strtof(), and strtold() functions  are  thread-safe  with
       exceptions.  These functions can be safely used in multithreaded appli-
       cations, as long as setlocale(3) is not called  to  change  the  locale
       during their execution.

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  deter-
       mine if an error occurred by checking whether errno has a nonzero value
       after the call.

       In the glibc implementation, the n-char-sequence that  optionally  fol-
       lows "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  man-
       tissa component of the returned value.

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), nan(3), nanf(3),  nanl(3),  strtol(3),  str-
       toul(3)

COLOPHON
       This  page  is  part of release 3.71 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at
       http://www.kernel.org/doc/man-pages/.

Linux                             2014-08-19                         STRTOD(3)

Man(1) output converted with man2html
list of all man pages