<?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 Lesser General Public License as published by the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details. You should have received a copy of the GNU Lesser 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> <refname>sd_is_special</refname> <refpurpose>Check the type of a file descriptor</refpurpose> </refnamediv> <refsynopsisdiv> <funcsynopsis> <funcsynopsisinfo>#include <systemd/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> <funcprototype> <funcdef>int <function>sd_is_special</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 <constant>NULL</constant>, 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. If the <parameter>family</parameter> parameter is not <constant>AF_UNSPEC</constant>, it is checked whether the socket is of the specified family (AF_UNIX, <constant>AF_INET</constant>, ...). If the <parameter>type</parameter> parameter is not 0, it is checked whether the socket is of the specified type (<constant>SOCK_STREAM</constant>, <constant>SOCK_DGRAM</constant>, ...). 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 <constant>AF_UNSPEC</constant>, <constant>AF_INET</constant>, or <constant>AF_INET6</constant>.</para> <para><function>sd_is_socket_unix()</function> is similar to <function>sd_is_socket()</function> but optionally checks the <constant>AF_UNIX</constant> path the socket is bound to, unless the <parameter>path</parameter> parameter is <constant>NULL</constant>. For normal file system <constant>AF_UNIX</constant> 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 the <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 <constant>NULL</constant>, it is checked whether the message queue is bound to the specified name.</para> <para><function>sd_is_special()</function> may be called to check whether the specified file descriptor refers to a special file. If the <parameter>path</parameter> parameter is not <constant>NULL</constant>, it is checked whether file descriptor is bound to the specified file name. Special files in this context are character device nodes and files in <filename>/proc</filename> or <filename>/sys</filename>.</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 they 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 algorithms, check the liberally licensed reference implementation sources: <ulink url="http://cgit.freedesktop.org/systemd/systemd/plain/src/libsystemd-daemon/sd-daemon.c"/> and <ulink url="http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-daemon.h"/></para> <para><function>sd_is_fifo()</function> and the related functions are implemented in the reference implementation's <filename>sd-daemon.c</filename> and <filename>sd-daemon.h</filename> files. These interfaces are available as shared library, which can be compiled and linked to with the <constant>libsystemd-daemon</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> file. Alternatively, applications consuming these APIs may copy the implementation into their source tree. For more details about the reference implementation see <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</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>3</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>