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sd_is_fifo.xml
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sd_is_fifo.xml
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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
<refentry id="sd_is_fifo"
xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_is_fifo</title>
<productname>systemd</productname>
</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_socket_sockaddr</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_sockaddr</function></funcdef>
<paramdef>int <parameter>fd</parameter></paramdef>
<paramdef>int <parameter>type</parameter></paramdef>
<paramdef>const struct sockaddr *<parameter>addr</parameter></paramdef>
<paramdef>unsigned <parameter>addr_len</parameter></paramdef>
<paramdef>int <parameter>listening</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 (<constant>AF_UNIX</constant>,
<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_sockaddr()</function> is similar to
<function>sd_is_socket_inet()</function>, but checks if the socket is bound to the
address specified by <parameter>addr</parameter>. The
<structfield>family</structfield> specified by <parameter>addr</parameter> must be
either <constant>AF_INET</constant> or <constant>AF_INET6</constant> and
<parameter>addr_len</parameter> must be large enough for that family. If
<parameter>addr</parameter> specifies a non-zero port, it is also checked if the
socket is bound to this port. In addition, for IPv6, if <parameter>addr</parameter>
specifies non-zero <structfield>sin6_flowinfo</structfield> or
<structfield>sin6_scope_id</structfield>, it is checked if the socket has the same
values.</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 the file
descriptor is bound to the specified filename. 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>
<xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>
<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>
</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>,
<citerefentry project='man-pages'><refentrytitle>ip</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>ipv6</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>unix</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>fifo</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>mq_overview</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
<citerefentry project='man-pages'><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
</para>
</refsect1>
</refentry>