diff options
Diffstat (limited to 'man/sd_bus_new.xml')
| -rw-r--r-- | man/sd_bus_new.xml | 204 |
1 files changed, 204 insertions, 0 deletions
diff --git a/man/sd_bus_new.xml b/man/sd_bus_new.xml new file mode 100644 index 0000000..cc08e6b --- /dev/null +++ b/man/sd_bus_new.xml @@ -0,0 +1,204 @@ +<?xml version='1.0'?> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" +"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> + +<!-- + SPDX-License-Identifier: LGPL-2.1+ +--> + +<refentry id="sd_bus_new" xmlns:xi="http://www.w3.org/2001/XInclude"> + + <refentryinfo> + <title>sd_bus_new</title> + <productname>systemd</productname> + </refentryinfo> + + <refmeta> + <refentrytitle>sd_bus_new</refentrytitle> + <manvolnum>3</manvolnum> + </refmeta> + + <refnamediv> + <refname>sd_bus_new</refname> + <refname>sd_bus_ref</refname> + <refname>sd_bus_unref</refname> + <refname>sd_bus_unrefp</refname> + <refname>sd_bus_close_unref</refname> + <refname>sd_bus_close_unrefp</refname> + <refname>sd_bus_flush_close_unref</refname> + <refname>sd_bus_flush_close_unrefp</refname> + + <refpurpose>Create a new bus object and create or destroy references to it</refpurpose> + </refnamediv> + + <refsynopsisdiv> + <funcsynopsis> + <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> + + <funcprototype> + <funcdef>int <function>sd_bus_new</function></funcdef> + <paramdef>sd_bus **<parameter>bus</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>sd_bus *<function>sd_bus_ref</function></funcdef> + <paramdef>sd_bus *<parameter>bus</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>sd_bus *<function>sd_bus_unref</function></funcdef> + <paramdef>sd_bus *<parameter>bus</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>sd_bus *<function>sd_bus_close_unref</function></funcdef> + <paramdef>sd_bus *<parameter>bus</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>sd_bus *<function>sd_bus_flush_close_unref</function></funcdef> + <paramdef>sd_bus *<parameter>bus</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>void <function>sd_bus_unrefp</function></funcdef> + <paramdef>sd_bus **<parameter>busp</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>void <function>sd_bus_close_unrefp</function></funcdef> + <paramdef>sd_bus **<parameter>busp</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>void <function>sd_bus_flush_close_unrefp</function></funcdef> + <paramdef>sd_bus **<parameter>busp</parameter></paramdef> + </funcprototype> + </funcsynopsis> + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + + <para><function>sd_bus_new()</function> creates a new bus + object. This object is reference-counted, and will be destroyed + when all references are gone. Initially, the caller of this + function owns the sole reference and the bus object will not be + connected to any bus. To connect it to a bus, make sure + to set an address with + <citerefentry><refentrytitle>sd_bus_set_address</refentrytitle><manvolnum>3</manvolnum></citerefentry> + or a related call, and then start the connection with + <citerefentry><refentrytitle>sd_bus_start</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> + + <para>In most cases, it is a better idea to invoke + <citerefentry><refentrytitle>sd_bus_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry> + or related calls instead of the more low-level + <function>sd_bus_new()</function> and + <function>sd_bus_start()</function>. The higher-level calls not + only allocate a bus object but also start the connection to a + well-known bus in a single function invocation.</para> + + <para><function>sd_bus_ref()</function> increases the reference + counter of <parameter>bus</parameter> by one.</para> + + <para><function>sd_bus_unref()</function> decreases the reference + counter of <parameter>bus</parameter> by one. Once the reference + count has dropped to zero, <parameter>bus</parameter> is destroyed + and cannot be used anymore, so further calls to + <function>sd_bus_ref()</function> or + <function>sd_bus_unref()</function> are illegal.</para> + + <para><function>sd_bus_unrefp()</function> is similar to + <function>sd_bus_unref()</function> but takes a pointer to a + pointer to an <type>sd_bus</type> object. This call is useful in + conjunction with GCC's and LLVM's <ulink + url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up + Variable Attribute</ulink>. Note that this function is defined as + inline function. Use a declaration like the following, in order to + allocate a bus object that is freed automatically as the code + block is left:</para> + + <programlisting>{ + __attribute__((cleanup(sd_bus_unrefp)) sd_bus *bus = NULL; + int r; + … + r = sd_bus_default(&bus); + if (r < 0) + fprintf(stderr, "Failed to allocate bus: %s\n", strerror(-r)); + … +}</programlisting> + + <para><function>sd_bus_ref()</function> and <function>sd_bus_unref()</function> + execute no operation if the passed in bus object address is + <constant>NULL</constant>. <function>sd_bus_unrefp()</function> will first + dereference its argument, which must not be <constant>NULL</constant>, and will + execute no operation if <emphasis>that</emphasis> is <constant>NULL</constant>. + </para> + + <para><function>sd_bus_close_unref()</function> is similar to <function>sd_bus_unref()</function>, but + first executes + <citerefentry><refentrytitle>sd_bus_close</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + ensuring that the connection is terminated before the reference to the connection is dropped and possibly + the object freed.</para> + + <para><function>sd_bus_flush_close_unref()</function> is similar to <function>sd_bus_unref()</function>, + but first executes + <citerefentry><refentrytitle>sd_bus_flush</refentrytitle><manvolnum>3</manvolnum></citerefentry> as well + as <citerefentry><refentrytitle>sd_bus_close</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + ensuring that any pending messages are synchronously flushed out before the reference to the connection + is dropped and possibly the object freed. This call is particularly useful immediately before exiting + from a program as it ensures that any pending outgoing messages are written out, and unprocessed but + queued incoming messages released before the connection is terminated and released.</para> + + <para><function>sd_bus_close_unrefp()</function> is similar to + <function>sd_bus_close_unref()</function>, but may be used in GCC's and LLVM's Clean-up Variable + Attribute, see above. Similarly, <function>sd_bus_flush_close_unrefp()</function> is similar to + <function>sd_bus_flush_close_unref()</function>.</para> + </refsect1> + + <refsect1> + <title>Return Value</title> + + <para>On success, <function>sd_bus_new()</function> returns 0 or a + positive integer. On failure, it returns a negative errno-style + error code.</para> + + <para><function>sd_bus_ref()</function> always returns the argument. + </para> + + <para><function>sd_bus_unref()</function> and <function>sd_bus_flush_close_unref()</function> always return + <constant>NULL</constant>.</para> + </refsect1> + + <refsect1> + <title>Errors</title> + + <para>Returned errors may indicate the following problems:</para> + + <variablelist> + <varlistentry> + <term><constant>-ENOMEM</constant></term> + + <listitem><para>Memory allocation failed.</para></listitem> + </varlistentry> + </variablelist> + </refsect1> + + <xi:include href="libsystemd-pkgconfig.xml" /> + + <refsect1> + <title>See Also</title> + + <para> + <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd_bus_default_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd_bus_default_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd_bus_open_user</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd_bus_open_system</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd_bus_close</refentrytitle><manvolnum>3</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |