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 .