path: root/templates/man7/epoll.7.pot

# SOME DESCRIPTIVE TITLE
# Copyright (C) YEAR Free Software Foundation, Inc.
# This file is distributed under the same license as the PACKAGE package.
# FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
#
#, fuzzy
msgid ""
msgstr ""
"Project-Id-Version: PACKAGE VERSION\n"
"POT-Creation-Date: 2024-06-01 05:48+0200\n"
"PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
"Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
"Language-Team: LANGUAGE <LL@li.org>\n"
"Language: \n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=UTF-8\n"
"Content-Transfer-Encoding: 8bit\n"

#. type: TH
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "epoll"
msgstr ""

#. type: TH
#: archlinux debian-unstable opensuse-tumbleweed
#, no-wrap
msgid "2024-05-02"
msgstr ""

#. type: TH
#: archlinux debian-unstable
#, no-wrap
msgid "Linux man-pages 6.8"
msgstr ""

#. type: SH
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "NAME"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid "epoll - I/O event notification facility"
msgstr ""

#. type: SH
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "SYNOPSIS"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "B<#include E<lt>sys/epoll.hE<gt>>\n"
msgstr ""

#. type: SH
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "DESCRIPTION"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"The B<epoll> API performs a similar task to B<poll>(2): monitoring multiple "
"file descriptors to see if I/O is possible on any of them.  The B<epoll> API "
"can be used either as an edge-triggered or a level-triggered interface and "
"scales well to large numbers of watched file descriptors."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"The central concept of the B<epoll> API is the B<epoll> I<instance>, an in-"
"kernel data structure which, from a user-space perspective, can be "
"considered as a container for two lists:"
msgstr ""

#. type: IP
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "\\[bu]"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"The I<interest> list (sometimes also called the B<epoll> set): the set of "
"file descriptors that the process has registered an interest in monitoring."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"The I<ready> list: the set of file descriptors that are \"ready\" for I/O.  "
"The ready list is a subset of (or, more precisely, a set of references to)  "
"the file descriptors in the interest list.  The ready list is dynamically "
"populated by the kernel as a result of I/O activity on those file "
"descriptors."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"The following system calls are provided to create and manage an B<epoll> "
"instance:"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"B<epoll_create>(2)  creates a new B<epoll> instance and returns a file "
"descriptor referring to that instance.  (The more recent "
"B<epoll_create1>(2)  extends the functionality of B<epoll_create>(2).)"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"Interest in particular file descriptors is then registered via "
"B<epoll_ctl>(2), which adds items to the interest list of the B<epoll> "
"instance."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"B<epoll_wait>(2)  waits for I/O events, blocking the calling thread if no "
"events are currently available.  (This system call can be thought of as "
"fetching items from the ready list of the B<epoll> instance.)"
msgstr ""

#. type: SS
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "Level-triggered and edge-triggered"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"The B<epoll> event distribution interface is able to behave both as edge-"
"triggered (ET) and as level-triggered (LT).  The difference between the two "
"mechanisms can be described as follows.  Suppose that this scenario happens:"
msgstr ""

#. type: IP
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "(1)"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"The file descriptor that represents the read side of a pipe (I<rfd>)  is "
"registered on the B<epoll> instance."
msgstr ""

#. type: IP
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "(2)"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid "A pipe writer writes 2\\ kB of data on the write side of the pipe."
msgstr ""

#. type: IP
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "(3)"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"A call to B<epoll_wait>(2)  is done that will return I<rfd> as a ready file "
"descriptor."
msgstr ""

#. type: IP
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "(4)"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid "The pipe reader reads 1\\ kB of data from I<rfd>."
msgstr ""

#. type: IP
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "(5)"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid "A call to B<epoll_wait>(2)  is done."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"If the I<rfd> file descriptor has been added to the B<epoll> interface using "
"the B<EPOLLET> (edge-triggered)  flag, the call to B<epoll_wait>(2)  done in "
"step B<5> will probably hang despite the available data still present in the "
"file input buffer; meanwhile the remote peer might be expecting a response "
"based on the data it already sent.  The reason for this is that edge-"
"triggered mode delivers events only when changes occur on the monitored file "
"descriptor.  So, in step B<5> the caller might end up waiting for some data "
"that is already present inside the input buffer.  In the above example, an "
"event on I<rfd> will be generated because of the write done in B<2> and the "
"event is consumed in B<3>.  Since the read operation done in B<4> does not "
"consume the whole buffer data, the call to B<epoll_wait>(2)  done in step "
"B<5> might block indefinitely."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"An application that employs the B<EPOLLET> flag should use nonblocking file "
"descriptors to avoid having a blocking read or write starve a task that is "
"handling multiple file descriptors.  The suggested way to use B<epoll> as an "
"edge-triggered (B<EPOLLET>)  interface is as follows:"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid "with nonblocking file descriptors; and"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"by waiting for an event only after B<read>(2)  or B<write>(2)  return "
"B<EAGAIN>."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"By contrast, when used as a level-triggered interface (the default, when "
"B<EPOLLET> is not specified), B<epoll> is simply a faster B<poll>(2), and "
"can be used wherever the latter is used since it shares the same semantics."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"Since even with edge-triggered B<epoll>, multiple events can be generated "
"upon receipt of multiple chunks of data, the caller has the option to "
"specify the B<EPOLLONESHOT> flag, to tell B<epoll> to disable the associated "
"file descriptor after the receipt of an event with B<epoll_wait>(2).  When "
"the B<EPOLLONESHOT> flag is specified, it is the caller's responsibility to "
"rearm the file descriptor using B<epoll_ctl>(2)  with B<EPOLL_CTL_MOD>."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"If multiple threads (or processes, if child processes have inherited the "
"B<epoll> file descriptor across B<fork>(2))  are blocked in "
"B<epoll_wait>(2)  waiting on the same epoll file descriptor and a file "
"descriptor in the interest list that is marked for edge-triggered "
"(B<EPOLLET>)  notification becomes ready, just one of the threads (or "
"processes) is awoken from B<epoll_wait>(2).  This provides a useful "
"optimization for avoiding \"thundering herd\" wake-ups in some scenarios."
msgstr ""

#. type: SS
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "Interaction with autosleep"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"If the system is in B<autosleep> mode via I</sys/power/autosleep> and an "
"event happens which wakes the device from sleep, the device driver will keep "
"the device awake only until that event is queued.  To keep the device awake "
"until the event has been processed, it is necessary to use the "
"B<epoll_ctl>(2)  B<EPOLLWAKEUP> flag."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"When the B<EPOLLWAKEUP> flag is set in the B<events> field for a I<struct "
"epoll_event>, the system will be kept awake from the moment the event is "
"queued, through the B<epoll_wait>(2)  call which returns the event until the "
"subsequent B<epoll_wait>(2)  call.  If the event should keep the system "
"awake beyond that time, then a separate I<wake_lock> should be taken before "
"the second B<epoll_wait>(2)  call."
msgstr ""

#. type: SS
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "/proc interfaces"
msgstr ""

#.  Following was added in Linux 2.6.28, but them removed in Linux 2.6.29
#.  .TP
#.  .IR /proc/sys/fs/epoll/max_user_instances " (since Linux 2.6.28)"
#.  This specifies an upper limit on the number of epoll instances
#.  that can be created per real user ID.
#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"The following interfaces can be used to limit the amount of kernel memory "
"consumed by epoll:"
msgstr ""

#. type: TP
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "I</proc/sys/fs/epoll/max_user_watches> (since Linux 2.6.28)"
msgstr ""

#.  Linux 2.6.29 (in Linux 2.6.28, the default was 1/32 of lowmem)
#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"This specifies a limit on the total number of file descriptors that a user "
"can register across all epoll instances on the system.  The limit is per "
"real user ID.  Each registered file descriptor costs roughly 90 bytes on a "
"32-bit kernel, and roughly 160 bytes on a 64-bit kernel.  Currently, the "
"default value for I<max_user_watches> is 1/25 (4%) of the available low "
"memory, divided by the registration cost in bytes."
msgstr ""

#. type: SS
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "Example for suggested usage"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"While the usage of B<epoll> when employed as a level-triggered interface "
"does have the same semantics as B<poll>(2), the edge-triggered usage "
"requires more clarification to avoid stalls in the application event loop.  "
"In this example, listener is a nonblocking socket on which B<listen>(2)  has "
"been called.  The function I<do_use_fd()> uses the new ready file descriptor "
"until B<EAGAIN> is returned by either B<read>(2)  or B<write>(2).  An event-"
"driven state machine application should, after having received B<EAGAIN>, "
"record its current state so that at the next call to I<do_use_fd()> it will "
"continue to B<read>(2)  or B<write>(2)  from where it stopped before."
msgstr ""

#. type: Plain text
#: archlinux debian-unstable fedora-40 fedora-rawhide mageia-cauldron
#: opensuse-tumbleweed
#, no-wrap
msgid ""
"#define MAX_EVENTS 10\n"
"struct epoll_event ev, events[MAX_EVENTS];\n"
"int listen_sock, conn_sock, nfds, epollfd;\n"
"\\&\n"
"/* Code to set up listening socket, \\[aq]listen_sock\\[aq],\n"
"   (socket(), bind(), listen()) omitted. */\n"
"\\&\n"
"epollfd = epoll_create1(0);\n"
"if (epollfd == -1) {\n"
"    perror(\"epoll_create1\");\n"
"    exit(EXIT_FAILURE);\n"
"}\n"
"\\&\n"
"ev.events = EPOLLIN;\n"
"ev.data.fd = listen_sock;\n"
"if (epoll_ctl(epollfd, EPOLL_CTL_ADD, listen_sock, &ev) == -1) {\n"
"    perror(\"epoll_ctl: listen_sock\");\n"
"    exit(EXIT_FAILURE);\n"
"}\n"
"\\&\n"
"for (;;) {\n"
"    nfds = epoll_wait(epollfd, events, MAX_EVENTS, -1);\n"
"    if (nfds == -1) {\n"
"        perror(\"epoll_wait\");\n"
"        exit(EXIT_FAILURE);\n"
"    }\n"
"\\&\n"
"    for (n = 0; n E<lt> nfds; ++n) {\n"
"        if (events[n].data.fd == listen_sock) {\n"
"            conn_sock = accept(listen_sock,\n"
"                               (struct sockaddr *) &addr, &addrlen);\n"
"            if (conn_sock == -1) {\n"
"                perror(\"accept\");\n"
"                exit(EXIT_FAILURE);\n"
"            }\n"
"            setnonblocking(conn_sock);\n"
"            ev.events = EPOLLIN | EPOLLET;\n"
"            ev.data.fd = conn_sock;\n"
"            if (epoll_ctl(epollfd, EPOLL_CTL_ADD, conn_sock,\n"
"                        &ev) == -1) {\n"
"                perror(\"epoll_ctl: conn_sock\");\n"
"                exit(EXIT_FAILURE);\n"
"            }\n"
"        } else {\n"
"            do_use_fd(events[n].data.fd);\n"
"        }\n"
"    }\n"
"}\n"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"When used as an edge-triggered interface, for performance reasons, it is "
"possible to add the file descriptor inside the B<epoll> interface "
"(B<EPOLL_CTL_ADD>)  once by specifying (B<EPOLLIN>|B<EPOLLOUT>).  This "
"allows you to avoid continuously switching between B<EPOLLIN> and "
"B<EPOLLOUT> calling B<epoll_ctl>(2)  with B<EPOLL_CTL_MOD>."
msgstr ""

#. type: SS
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "Questions and answers"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"What is the key used to distinguish the file descriptors registered in an "
"interest list?"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"The key is the combination of the file descriptor number and the open file "
"description (also known as an \"open file handle\", the kernel's internal "
"representation of an open file)."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"What happens if you register the same file descriptor on an B<epoll> "
"instance twice?"
msgstr ""

#
#
#.  But a file descriptor duplicated by fork(2) can't be added to the
#.  set, because the [file *, fd] pair is already in the epoll set.
#.  That is a somewhat ugly inconsistency.  On the one hand, a child process
#.  cannot add the duplicate file descriptor to the epoll set.  (In every
#.  other case that I can think of, file descriptors duplicated by fork have
#.  similar semantics to file descriptors duplicated by dup() and friends.)  On
#.  the other hand, the very fact that the child has a duplicate of the
#.  file descriptor means that even if the parent closes its file descriptor,
#.  then epoll_wait() in the parent will continue to receive notifications for
#.  that file descriptor because of the duplicated file descriptor in the child.
#.  See http://thread.gmane.org/gmane.linux.kernel/596462/
#.  "epoll design problems with common fork/exec patterns"
#.  mtk, Feb 2008
#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"You will probably get B<EEXIST>.  However, it is possible to add a duplicate "
"(B<dup>(2), B<dup2>(2), B<fcntl>(2)  B<F_DUPFD>)  file descriptor to the "
"same B<epoll> instance.  This can be a useful technique for filtering "
"events, if the duplicate file descriptors are registered with different "
"I<events> masks."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"Can two B<epoll> instances wait for the same file descriptor? If so, are "
"events reported to both B<epoll> file descriptors?"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"Yes, and events would be reported to both.  However, careful programming may "
"be needed to do this correctly."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid "Is the B<epoll> file descriptor itself poll/epoll/selectable?"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"Yes.  If an B<epoll> file descriptor has events waiting, then it will "
"indicate as being readable."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"What happens if one attempts to put an B<epoll> file descriptor into its own "
"file descriptor set?"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"The B<epoll_ctl>(2)  call fails (B<EINVAL>).  However, you can add an "
"B<epoll> file descriptor inside another B<epoll> file descriptor set."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"Can I send an B<epoll> file descriptor over a UNIX domain socket to another "
"process?"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"Yes, but it does not make sense to do this, since the receiving process "
"would not have copies of the file descriptors in the interest list."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"Will closing a file descriptor cause it to be removed from all B<epoll> "
"interest lists?"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"Yes, but be aware of the following point.  A file descriptor is a reference "
"to an open file description (see B<open>(2)).  Whenever a file descriptor is "
"duplicated via B<dup>(2), B<dup2>(2), B<fcntl>(2)  B<F_DUPFD>, or "
"B<fork>(2), a new file descriptor referring to the same open file "
"description is created.  An open file description continues to exist until "
"all file descriptors referring to it have been closed."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"A file descriptor is removed from an interest list only after all the file "
"descriptors referring to the underlying open file description have been "
"closed.  This means that even after a file descriptor that is part of an "
"interest list has been closed, events may be reported for that file "
"descriptor if other file descriptors referring to the same underlying file "
"description remain open.  To prevent this happening, the file descriptor "
"must be explicitly removed from the interest list (using B<epoll_ctl>(2)  "
"B<EPOLL_CTL_DEL>)  before it is duplicated.  Alternatively, the application "
"must ensure that all file descriptors are closed (which may be difficult if "
"file descriptors were duplicated behind the scenes by library functions that "
"used B<dup>(2)  or B<fork>(2))."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"If more than one event occurs between B<epoll_wait>(2)  calls, are they "
"combined or reported separately?"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid "They will be combined."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"Does an operation on a file descriptor affect the already collected but not "
"yet reported events?"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"You can do two operations on an existing file descriptor.  Remove would be "
"meaningless for this case.  Modify will reread available I/O."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"Do I need to continuously read/write a file descriptor until B<EAGAIN> when "
"using the B<EPOLLET> flag (edge-triggered behavior)?"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"Receiving an event from B<epoll_wait>(2)  should suggest to you that such "
"file descriptor is ready for the requested I/O operation.  You must consider "
"it ready until the next (nonblocking)  read/write yields B<EAGAIN>.  When "
"and how you will use the file descriptor is entirely up to you."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"For packet/token-oriented files (e.g., datagram socket, terminal in "
"canonical mode), the only way to detect the end of the read/write I/O space "
"is to continue to read/write until B<EAGAIN>."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"For stream-oriented files (e.g., pipe, FIFO, stream socket), the condition "
"that the read/write I/O space is exhausted can also be detected by checking "
"the amount of data read from / written to the target file descriptor.  For "
"example, if you call B<read>(2)  by asking to read a certain amount of data "
"and B<read>(2)  returns a lower number of bytes, you can be sure of having "
"exhausted the read I/O space for the file descriptor.  The same is true when "
"writing using B<write>(2).  (Avoid this latter technique if you cannot "
"guarantee that the monitored file descriptor always refers to a stream-"
"oriented file.)"
msgstr ""

#. type: SS
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "Possible pitfalls and ways to avoid them"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid "B<Starvation (edge-triggered)>"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"If there is a large amount of I/O space, it is possible that by trying to "
"drain it the other files will not get processed causing starvation.  (This "
"problem is not specific to B<epoll>.)"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"The solution is to maintain a ready list and mark the file descriptor as "
"ready in its associated data structure, thereby allowing the application to "
"remember which files need to be processed but still round robin amongst all "
"the ready files.  This also supports ignoring subsequent events you receive "
"for file descriptors that are already ready."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid "B<If using an event cache...>"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"If you use an event cache or store all the file descriptors returned from "
"B<epoll_wait>(2), then make sure to provide a way to mark its closure "
"dynamically (i.e., caused by a previous event's processing).  Suppose you "
"receive 100 events from B<epoll_wait>(2), and in event #47 a condition "
"causes event #13 to be closed.  If you remove the structure and B<close>(2)  "
"the file descriptor for event #13, then your event cache might still say "
"there are events waiting for that file descriptor causing confusion."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"One solution for this is to call, during the processing of event 47, "
"B<epoll_ctl>(B<EPOLL_CTL_DEL>)  to delete file descriptor 13 and "
"B<close>(2), then mark its associated data structure as removed and link it "
"to a cleanup list.  If you find another event for file descriptor 13 in your "
"batch processing, you will discover the file descriptor had been previously "
"removed and there will be no confusion."
msgstr ""

#. type: SH
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "VERSIONS"
msgstr ""

#. type: Plain text
#: archlinux debian-unstable fedora-40 fedora-rawhide mageia-cauldron
#: opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"Some other systems provide similar mechanisms; for example, FreeBSD has "
"I<kqueue>, and Solaris has I</dev/poll>."
msgstr ""

#. type: SH
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "STANDARDS"
msgstr ""

#. type: Plain text
#: archlinux debian-unstable fedora-40 fedora-rawhide mageia-cauldron
#: opensuse-leap-15-6 opensuse-tumbleweed
msgid "Linux."
msgstr ""

#. type: SH
#: archlinux debian-unstable fedora-40 fedora-rawhide mageia-cauldron
#: opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "HISTORY"
msgstr ""

#.  Its interface should be finalized in Linux 2.5.66.
#. type: Plain text
#: archlinux debian-unstable fedora-40 fedora-rawhide mageia-cauldron
#: opensuse-leap-15-6 opensuse-tumbleweed
msgid "Linux 2.5.44.  glibc 2.3.2."
msgstr ""

#. type: SH
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "NOTES"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"The set of file descriptors that is being monitored via an epoll file "
"descriptor can be viewed via the entry for the epoll file descriptor in the "
"process's I</proc/>pidI</fdinfo> directory.  See B<proc>(5)  for further "
"details."
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"The B<kcmp>(2)  B<KCMP_EPOLL_TFD> operation can be used to test whether a "
"file descriptor is present in an epoll instance."
msgstr ""

#. type: SH
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
#, no-wrap
msgid "SEE ALSO"
msgstr ""

#. type: Plain text
#: archlinux debian-bookworm debian-unstable fedora-40 fedora-rawhide
#: mageia-cauldron opensuse-leap-15-6 opensuse-tumbleweed
msgid ""
"B<epoll_create>(2), B<epoll_create1>(2), B<epoll_ctl>(2), B<epoll_wait>(2), "
"B<poll>(2), B<select>(2)"
msgstr ""

#. type: TH
#: debian-bookworm
#, no-wrap
msgid "2023-02-05"
msgstr ""

#. type: TH
#: debian-bookworm
#, no-wrap
msgid "Linux man-pages 6.03"
msgstr ""

#. type: Plain text
#: debian-bookworm opensuse-leap-15-6
#, no-wrap
msgid ""
"#define MAX_EVENTS 10\n"
"struct epoll_event ev, events[MAX_EVENTS];\n"
"int listen_sock, conn_sock, nfds, epollfd;\n"
msgstr ""

#. type: Plain text
#: debian-bookworm opensuse-leap-15-6
#, no-wrap
msgid ""
"/* Code to set up listening socket, \\[aq]listen_sock\\[aq],\n"
"   (socket(), bind(), listen()) omitted. */\n"
msgstr ""

#. type: Plain text
#: debian-bookworm opensuse-leap-15-6
#, no-wrap
msgid ""
"epollfd = epoll_create1(0);\n"
"if (epollfd == -1) {\n"
"    perror(\"epoll_create1\");\n"
"    exit(EXIT_FAILURE);\n"
"}\n"
msgstr ""

#. type: Plain text
#: debian-bookworm opensuse-leap-15-6
#, no-wrap
msgid ""
"ev.events = EPOLLIN;\n"
"ev.data.fd = listen_sock;\n"
"if (epoll_ctl(epollfd, EPOLL_CTL_ADD, listen_sock, &ev) == -1) {\n"
"    perror(\"epoll_ctl: listen_sock\");\n"
"    exit(EXIT_FAILURE);\n"
"}\n"
msgstr ""

#. type: Plain text
#: debian-bookworm opensuse-leap-15-6
#, no-wrap
msgid ""
"for (;;) {\n"
"    nfds = epoll_wait(epollfd, events, MAX_EVENTS, -1);\n"
"    if (nfds == -1) {\n"
"        perror(\"epoll_wait\");\n"
"        exit(EXIT_FAILURE);\n"
"    }\n"
msgstr ""

#. type: Plain text
#: debian-bookworm opensuse-leap-15-6
#, no-wrap
msgid ""
"    for (n = 0; n E<lt> nfds; ++n) {\n"
"        if (events[n].data.fd == listen_sock) {\n"
"            conn_sock = accept(listen_sock,\n"
"                               (struct sockaddr *) &addr, &addrlen);\n"
"            if (conn_sock == -1) {\n"
"                perror(\"accept\");\n"
"                exit(EXIT_FAILURE);\n"
"            }\n"
"            setnonblocking(conn_sock);\n"
"            ev.events = EPOLLIN | EPOLLET;\n"
"            ev.data.fd = conn_sock;\n"
"            if (epoll_ctl(epollfd, EPOLL_CTL_ADD, conn_sock,\n"
"                        &ev) == -1) {\n"
"                perror(\"epoll_ctl: conn_sock\");\n"
"                exit(EXIT_FAILURE);\n"
"            }\n"
"        } else {\n"
"            do_use_fd(events[n].data.fd);\n"
"        }\n"
"    }\n"
"}\n"
msgstr ""

#.  Its interface should be finalized in Linux kernel 2.5.66.
#. type: Plain text
#: debian-bookworm
msgid ""
"The B<epoll> API was introduced in Linux kernel 2.5.44.  Support was added "
"in glibc 2.3.2."
msgstr ""

#. type: Plain text
#: debian-bookworm
msgid ""
"The B<epoll> API is Linux-specific.  Some other systems provide similar "
"mechanisms, for example, FreeBSD has I<kqueue>, and Solaris has I</dev/poll>."
msgstr ""

#. type: TH
#: fedora-40 fedora-rawhide mageia-cauldron
#, no-wrap
msgid "2023-10-31"
msgstr ""

#. type: TH
#: fedora-40 mageia-cauldron
#, no-wrap
msgid "Linux man-pages 6.06"
msgstr ""

#. type: TH
#: fedora-rawhide
#, no-wrap
msgid "Linux man-pages 6.7"
msgstr ""

#. type: TH
#: opensuse-leap-15-6
#, no-wrap
msgid "2023-03-30"
msgstr ""

#. type: TH
#: opensuse-leap-15-6
#, no-wrap
msgid "Linux man-pages 6.04"
msgstr ""

#. type: TH
#: opensuse-tumbleweed
#, no-wrap
msgid "Linux man-pages (unreleased)"
msgstr ""