PROLOG

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

NAME

       posix_spawn_file_actions_adddup2 — add dup2 action to spawn file actions object (ADVANCED REALTIME)

SYNOPSIS

       #include <spawn.h>

       int posix_spawn_file_actions_adddup2(posix_spawn_file_actions_t
           *file_actions, int fildes, int newfildes);

DESCRIPTION

       The  posix_spawn_file_actions_adddup2()  function  shall  add a dup2() action to the object referenced by
       file_actions that shall  cause  the  file  descriptor  fildes  to  be  duplicated  as  newfildes  (as  if
       dup2(fildes, newfildes) had been called) when a new process is spawned using this file actions object.

       A spawn file actions object is as defined in posix_spawn_file_actions_addclose().

RETURN VALUE

       Upon successful completion, the posix_spawn_file_actions_adddup2() function shall return zero; otherwise,
       an error number shall be returned to indicate the error.

ERRORS

       The posix_spawn_file_actions_adddup2() function shall fail if:

       EBADF  The value specified by fildes or newfildes is negative or greater than or equal to {OPEN_MAX}.

       ENOMEM Insufficient memory exists to add to the spawn file actions object.

       The posix_spawn_file_actions_adddup2() function may fail if:

       EINVAL The value specified by file_actions is invalid.

       It    shall    not    be    considered    an    error   for   the   fildes   argument   passed   to   the
       posix_spawn_file_actions_adddup2() function  to  specify  a  file  descriptor  for  which  the  specified
       operation  could  not  be  performed  at  the  time of the call. Any such error will be detected when the
       associated file actions object is later used during a posix_spawn() or posix_spawnp() operation.

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       The posix_spawn_file_actions_adddup2() function is part of the Spawn option and need not be  provided  on
       all implementations.

       Implementations  may  use  file  descriptors  that  must  be inherited into child processes for the child
       process to remain conforming, such as for message catalog or tracing purposes. Therefore, an  application
       that  calls  posix_spawn_file_actions_adddup2()  with  an  arbitrary  integer  for  newfildes  risks non-
       conforming behavior, and this function can only portably be used to overwrite file descriptor values that
       the application has obtained through explicit actions, or for the three file descriptors corresponding to
       the standard file streams. In order to avoid a race condition of leaking an  unintended  file  descriptor
       into a child process, an application should consider opening all file descriptors with the FD_CLOEXEC bit
       set unless the file descriptor is intended to be inherited across exec.

RATIONALE

       Refer to the RATIONALE section in posix_spawn_file_actions_addclose().

FUTURE DIRECTIONS

       None.

SEE ALSO

       dup(), posix_spawn(), posix_spawn_file_actions_addclose(), posix_spawn_file_actions_destroy()

       The Base Definitions volume of POSIX.1‐2017, <spawn.h>

COPYRIGHT

       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              POSIX_SPAWN_FILE_ACTIONS_ADDDUP2(3POSIX)