units: simplify rescue.service and emergency.service (#5623)

[thirdparty/systemd.git] / man / sd_is_fifo.xml

<?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">

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<refentry id="sd_is_fifo"
  xmlns:xi="http://www.w3.org/2001/XInclude">

  <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_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 &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_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 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>

    <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>