<?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">

<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 &lt;systemd/sd-daemon.h&gt;</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. 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 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 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>