Man Epoll_wait en anglais
EPOLL_WAIT(2) Linux Programmer's Manual EPOLL_WAIT(2)
NAME
epoll_wait, epoll_pwait - wait for an I/O event on an epoll file
descriptor
SYNOPSIS
#include
int epoll_wait(int epfd, struct epoll_event *events,
int maxevents, int timeout);
int epoll_pwait(int epfd, struct epoll_event *events,
int maxevents, int timeout,
const sigset_t *sigmask);
DESCRIPTION
The epoll_wait() system call waits for events on the epoll file
descriptor epfd for a maximum time of timeout milliseconds. The memory
area pointed to by events will contain the events that will be avail-
able for the caller. Up to maxevents are returned by epoll_wait().
The maxevents argument must be greater than zero. Specifying a timeout
of -1 makes epoll_wait() wait indefinitely, while specifying a timeout
equal to zero makes epoll_wait() to return immediately even if no
events are available (return code equal to zero). The struct
epoll_event is defined as :
typedef union epoll_data {
void *ptr;
int fd;
uint32_t u32;
uint64_t u64;
} epoll_data_t;
struct epoll_event {
uint32_t events; /* Epoll events */
epoll_data_t data; /* User data variable */
};
The data of each returned structure will contain the same data the user
set with an epoll_ctl(2) (EPOLL_CTL_ADD,EPOLL_CTL_MOD) while the events
member will contain the returned event bit field.
epoll_pwait()
The relationship between epoll_wait() and epoll_pwait() is analogous to
the relationship between select(2) and pselect(2): like pselect(2),
epoll_pwait() allows an application to safely wait until either a file
descriptor becomes ready or until a signal is caught.
The following epoll_pwait() call:
ready = epoll_pwait(epfd, &events, maxevents, timeout, &sigmask);
is equivalent to atomically executing the following calls:
sigset_t origmask;
sigprocmask(SIG_SETMASK, &sigmask, &origmask);
ready = epoll_wait(epfd, &events, maxevents, timeout);
sigprocmask(SIG_SETMASK, &origmask, NULL);
The sigmask argument may be specified as NULL, in which case
epoll_pwait() is equivalent to epoll_wait().
RETURN VALUE
When successful, epoll_wait() returns the number of file descriptors
ready for the requested I/O, or zero if no file descriptor became ready
during the requested timeout milliseconds. When an error occurs,
epoll_wait() returns -1 and errno is set appropriately.
ERRORS
EBADF epfd is not a valid file descriptor.
EFAULT The memory area pointed to by events is not accessible with
write permissions.
EINTR The call was interrupted by a signal handler before any of the
requested events occurred or the timeout expired; see signal(7).
EINVAL epfd is not an epoll file descriptor, or maxevents is less than
or equal to zero.
VERSIONS
epoll_pwait() was added to Linux in kernel 2.6.19.
Glibc support for epoll_pwait() is provided starting with version 2.6.
CONFORMING TO
epoll_wait() is Linux-specific, and was introduced in kernel 2.5.44.
SEE ALSO
epoll_create(2), epoll_ctl(2), epoll(7)
COLOPHON
This page is part of release 3.05 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
Linux 2008-04-23 EPOLL_WAIT(2)
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