1.\" 2.\" Copyright (c) 2024 Rick Parrish <unitrunker@unitrunker.net> 3.\" 4.\" SPDX-License-Identifier: BSD-2-Clause 5.\" 6.Dd December 18, 2025 7.Dt MQ_GETFD_NP 3 8.Os 9.Sh NAME 10.Nm mq_getfd_np 11.Nd get a file descriptor for an open message queue descriptor 12.Sh SYNOPSIS 13.Lb librt 14.In mqueue.h 15.Ft int 16.Fn mq_getfd_np "mqd_t mqd" 17.Sh DESCRIPTION 18The 19.Nm 20function retrieves the underlying file descriptor 21from the given message queue descriptor returned from 22.Xr mq_open 2 . 23The file descriptor is used by other functions 24to refer to that message queue. 25The 26.Fa mqd 27argument must be an open message queue descriptor. 28.Sh IMPLEMENTATION NOTES 29.Fx 30implements retrieval or alteration of message queue attributes 31based on the file descriptor. 32The open file descriptor is copied into a child after 33.Xr fork 2 . 34The 35.Xr fstat 2 , 36.Xr fchmod 2 , 37and 38.Xr fchown 2 39system calls are supported for the file descriptor. 40.Pp 41The file descriptor is safe to use so long as 42the message queue descriptor remains open. 43.Sh RETURN VALUES 44Upon successful completion, the function returns a file descriptor. 45.Sh ERRORS 46The 47.Nm 48function does not return any errors. 49.Sh SEE ALSO 50.Xr mq_close 2 , 51.Xr mq_open 2 , 52.Xr mqueuefs 4 53.Sh HISTORY 54Support for the 55.Nm 56function first appeared in 57.Fx 11.0 . 58