posix_spawn_file_actions_addclose(3) on FreeBSD
The text 5f8f99deb553, as FreeBSD 15.0-RELEASE, FreeBSD 14.5-RELEASE, FreeBSD 14.4-RELEASE, FreeBSD 14.3-RELEASE, FreeBSD 14.2-RELEASE, FreeBSD 14.1-RELEASE shipped it.
add open, dup2, close, closefrom, or chdir/fchdir actions to spawn file actions object