FSETOWN(9)

FSETOWN(9) | Kernel Developer's Manual | FSETOWN(9)

# NAME

fsetown, fgetown, fownsignal — file descriptor owner handling functions

# SYNOPSIS

#include <sys/file.h>
int
fsetown(struct lwp *l, pid_t *pgid, int cmd, const void *data);
int
fgetown(struct lwp *l, pid_t pgid, int cmd, void *data);
void
fownsignal(pid_t pgid, int signo, int code, int band, void *fdescdata);

# DESCRIPTION

These functions handle file descriptor owner related ioctls and related signal delivery. Device drivers and other parts of the kernel call these functions from ioctl entry functions or I/O notification functions.
fsetown() sets the owner of file. cmd is an ioctl command, one of `SIOCSPGRP`, `FIOSETOWN`, and `TIOCSPGRP`. data is interpreted as a pointer to a signed integer, the integer being the ID of the owner. The cmd determines how exactly data should be interpreted. If cmd is `TIOCSPGRP`, the ID needs to be positive and is interpreted as process group ID. For `SIOCSPGRP` and `FIOSETOWN`, the passed ID is the process ID if positive, or the process group ID if negative.
fgetown() returns the current owner of the file. cmd is an ioctl command, one of `SIOCGPGRP`, `FIOGETOWN`, and `TIOCGPGRP`. data is interpreted as a pointer to a signed integer, and the value is set according to the passed cmd. For `TIOCGPGRP`, the returned data value is positive process group ID if the owner is the process group, or negative process ID if the owner is a process. For other ioctls, the returned value is the positive process ID if the owner is a process, or the negative process group ID if the owner is a process group.
fownsignal() schedules the signo signal to be sent to the current file descriptor owner. The signals typically used with this function are `SIGIO` and `SIGURG`. The code and band arguments are sent along with the signal as additional signal specific information if `SA_SIGINFO` is activated. If the information is not available from the context of the fownsignal() call, these should be passed as zero. fdescdata is used to lookup the file descriptor for `SA_SIGINFO` signals. If it is specified, the file descriptor number is sent along with the signal as additional signal specific information. If file descriptor data pointer is not available in the context of the fownsignal() call, `NULL` should be used instead.
Note that a fcntl(2) `F_SETOWN request` is translated by the kernel to a `FIOSETOWN` ioctl, and `F_GETOWN` is translated to `FIOGETOWN`. This is done transparently by generic code, before the device- or subsystem-specific ioctl entry function is called.

# SEE ALSO

fcntl(2), siginfo(2), signal(7), ioctl(9), signal(9)

# HISTORY

These kernel functions appeared in NetBSD 2.0.

December 20, 2005 | NetBSD 8.0