FWRITE(3)                  POSIX Programmer's Manual                 FWRITE(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
       fwrite -- binary output

SSYYNNOOPPSSIISS
       #include <stdio.h>

       size_t fwrite(const void *restrict _p_t_r, size_t _s_i_z_e, size_t _n_i_t_e_m_s,
           FILE *restrict _s_t_r_e_a_m);

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 _f_w_r_i_t_e() function shall write, from the array pointed to by _p_t_r, up
       to _n_i_t_e_m_s elements whose size is specified by _s_i_z_e, to the stream
       pointed to by _s_t_r_e_a_m.  For each object, _s_i_z_e calls shall be made to the
       _f_p_u_t_c() function, taking the values (in order) from an array of
       uunnssiiggnneedd cchhaarr exactly overlaying the object. The file-position
       indicator for the stream (if defined) shall be advanced by the number
       of bytes successfully written. If an error occurs, the resulting value
       of the file-position indicator for the stream is unspecified.

       The last data modification and last file status change timestamps of
       the file shall be marked for update between the successful execution of
       _f_w_r_i_t_e() and the next successful completion of a call to _f_f_l_u_s_h() or
       _f_c_l_o_s_e() on the same stream, or a call to _e_x_i_t() or _a_b_o_r_t().

RREETTUURRNN VVAALLUUEE
       The _f_w_r_i_t_e() function shall return the number of elements successfully
       written, which may be less than _n_i_t_e_m_s if a write error is encountered.
       If _s_i_z_e or _n_i_t_e_m_s is 0, _f_w_r_i_t_e() shall return 0 and the state of the
       stream remains unchanged. Otherwise, if a write error occurs, the error
       indicator for the stream shall be set, and _e_r_r_n_o shall be set to
       indicate the error.

EERRRROORRSS
       Refer to _f_p_u_t_c().

       _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
       Because of possible differences in element length and byte ordering,
       files written using _f_w_r_i_t_e() are application-dependent, and possibly
       cannot be read using _f_r_e_a_d() by a different application or by the same
       application on a different processor.

RRAATTIIOONNAALLEE
       None.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _S_e_c_t_i_o_n _2_._5, _S_t_a_n_d_a_r_d _I_/_O _S_t_r_e_a_m_s, _f_e_r_r_o_r(), _f_o_p_e_n(), _f_p_r_i_n_t_f(),
       _p_u_t_c(), _p_u_t_s(), _w_r_i_t_e()

       The Base Definitions volume of POSIX.1-2017, <<ssttddiioo..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                            FWRITE(3)
