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systemd/man/sd_is_fifo.xml
Lennart Poettering 916abb21d0 socket: add POSIX mqueue support
2011-05-17 19:37:03 +02:00

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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
This file is part of systemd.
Copyright 2010 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<refentry id="sd_is_fifo">
<refentryinfo>
<title>sd_is_fifo</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</refentryinfo>
<refmeta>
<refentrytitle>sd_is_fifo</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_is_fifo</refname>
<refname>sd_is_socket</refname>
<refname>sd_is_socket_inet</refname>
<refname>sd_is_socket_unix</refname>
<refname>sd_is_mq</refname>
<refpurpose>Check the type of a file descriptor</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include "sd-daemon.h"</funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_is_fifo</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>const char *<parameter>path</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_is_socket</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>int <parameter>family</parameter></paramdef>
<paramdef>int <parameter>type</parameter></paramdef>
<paramdef>int <parameter>listening</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_is_socket_inet</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>int <parameter>family</parameter></paramdef>
<paramdef>int <parameter>type</parameter></paramdef>
<paramdef>int <parameter>listening</parameter></paramdef>
<paramdef>uint16_t <parameter>port</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_is_socket_unix</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>int <parameter>type</parameter></paramdef>
<paramdef>int <parameter>listening</parameter></paramdef>
<paramdef>const char* <parameter>path</parameter></paramdef>
<paramdef>size_t <parameter>length</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_is_mq</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>const char *<parameter>path</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_is_fifo()</function> may be called
to check whether the specified file descriptor refers
to a FIFO or pipe. If the <parameter>path</parameter>
parameter is not NULL, it is checked whether the FIFO
is bound to the specified file system path.</para>
<para><function>sd_is_socket()</function> may be
called to check whether the specified file descriptor
refers to a socket. It the
<parameter>family</parameter> parameter is not
AF_UNSPEC it is checked whether the socket is of the
specified family (AF_UNIX, AF_INET, ...). If the
<parameter>type</parameter> parameter is not 0 it is
checked whether the socket is of the specified type
(SOCK_STREAM, SOCK_DGRAM, ...). If the
<parameter>listening</parameter> parameter is positive
it is checked whether the socket is in accepting mode,
i.e. <function>listen()</function> has been called for
it. If <parameter>listening</parameter> is 0, it is
checked whether the socket is not in this mode. If the
parameter is negative, no such check is made. The
<parameter>listening</parameter> parameter should only
be used for stream sockets and should be set to a
negative value otherwise.</para>
<para><function>sd_is_socket_inet()</function> is
similar to <function>sd_is_socket()</function>, but
optionally checks the IPv4 or IPv6 port number the
socket is bound to, unless <parameter>port</parameter>
is zero. For this call <parameter>family</parameter>
must be passed as either AF_UNSPEC, AF_INET or
AF_INET6.</para>
<para><function>sd_is_socket_unix()</function> is
similar to <function>sd_is_socket()</function>, but
optionally checks the AF_UNIX path the socket is bound
to, unless the <parameter>path</parameter> parameter
is NULL. For normal file system AF_UNIX sockets set
the <parameter>length</parameter> parameter to 0. For
Linux abstract namespace sockets set the
<parameter>length</parameter> to the size of the
address, including the initial 0 byte and set
<parameter>path</parameter> to the initial 0 byte of
the socket address.</para>
<para><function>sd_is_mq()</function> may be called to
check whether the specified file descriptor refers to
a POSIX message queue. If the
<parameter>path</parameter> parameter is not NULL, it
is checked whether the message queue is bound to the
specified name.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On failure, these calls return a negative
errno-style error code. If the file descriptor is of
the specified type and bound to the specified address
a positive return value is returned, otherwise
zero.</para>
</refsect1>
<refsect1>
<title>Notes</title>
<para>These functions are provided by the reference
implementation of APIs for new-style daemons and
distributed with the systemd package. The algorithms
they implement are simple, and can easily be
reimplemented in daemons if it is important to support
this interface without using the reference
implementation.</para>
<para>Internally, these function use a combination of
<filename>fstat()</filename> and
<filename>getsockname()</filename> to check the file
descriptor type and where it is bound to.</para>
<para>For details about the algorithm check the
liberally licensed reference implementation sources:
<ulink url="http://cgit.freedesktop.org/systemd/tree/src/sd-daemon.c"/>
resp. <ulink
url="http://cgit.freedesktop.org/systemd/tree/src/sd-daemon.h"/></para>
<para><function>sd_is_fifo()</function> and the
related functions are implemented in the reference
implementation's drop-in
<filename>sd-daemon.c</filename> and
<filename>sd-daemon.h</filename> files. It is
recommended that applications consuming these APIs
copy the implementation into their source tree. For
more details about the reference implementation see
<citerefentry><refentrytitle>sd_daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry></para>
<para>These functions continue to work as described,
even if -DDISABLE_SYSTEMD is set during
compilation.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>
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