ATOF(3)                    POSIX Programmer's Manual                   ATOF(3)



PPRROOLLOOGG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NNAAMMEE
       atof -- convert a string to a double-precision number

SSYYNNOOPPSSIISS
       #include <stdlib.h>

       double atof(const char *_s_t_r);

DDEESSCCRRIIPPTTIIOONN
       The functionality described on this reference page is aligned with the
       ISO C standard. Any conflict between the requirements described here
       and the ISO C standard is unintentional. This volume of POSIX.1-2017
       defers to the ISO C standard.

       The call _a_t_o_f(_s_t_r) shall be equivalent to:


           strtod(_s_t_r,(char **)NULL),

       except that the handling of errors may differ. If the value cannot be
       represented, the behavior is undefined.

RREETTUURRNN VVAALLUUEE
       The _a_t_o_f() function shall return the converted value if the value can
       be represented.

EERRRROORRSS
       No errors are defined.

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

EEXXAAMMPPLLEESS
       None.

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       The _a_t_o_f() function is subsumed by _s_t_r_t_o_d() but is retained because it
       is used extensively in existing code. If the number is not known to be
       in range, _s_t_r_t_o_d() should be used because _a_t_o_f() is not required to
       perform any error checking.

RRAATTIIOONNAALLEE
       None.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _s_t_r_t_o_d()

       The Base Definitions volume of POSIX.1-2017, <<ssttddlliibb..hh>>

CCOOPPYYRRIIGGHHTT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  In the event of any discrepancy between this version and the
       original IEEE and The Open Group Standard, the original IEEE and The
       Open Group Standard is the referee document. The original Standard can
       be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                              ATOF(3)
