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4afd3348c7
GLIB has recently started to officially support the gcc cleanup
attribute in its public API, hence let's do the same for our APIs.
With this patch we'll define an xyz_unrefp() call for each public
xyz_unref() call, to make it easy to use inside a
__attribute__((cleanup())) expression. Then, all code is ported over to
make use of this.
The new calls are also documented in the man pages, with examples how to
use them (well, I only added docs where the _unref() call itself already
had docs, and the examples, only cover sd_bus_unrefp() and
sd_event_unrefp()).
This also renames sd_lldp_free() to sd_lldp_unref(), since that's how we
tend to call our destructors these days.
Note that this defines no public macro that wraps gcc's attribute and
makes it easier to use. While I think it's our duty in the library to
make our stuff easy to use, I figure it's not our duty to make gcc's own
features easy to use on its own. Most likely, client code which wants to
make use of this should define its own:
#define _cleanup_(function) __attribute__((cleanup(function)))
Or similar, to make the gcc feature easier to use.
Making this logic public has the benefit that we can remove three header
files whose only purpose was to define these functions internally.
See #2008.
354 lines
15 KiB
XML
354 lines
15 KiB
XML
<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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This file is part of systemd.
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Copyright 2014 Zbigniew Jędrzejewski-Szmek
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="sd_bus_creds_new_from_pid">
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<refentryinfo>
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<title>sd_bus_creds_new_from_pid</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>A monkey with a typewriter</contrib>
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<firstname>Zbigniew</firstname>
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<surname>Jędrzejewski-Szmek</surname>
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<email>zbyszek@in.waw.pl</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_bus_creds_new_from_pid</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_bus_creds_new_from_pid</refname>
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<refname>sd_bus_creds_get_mask</refname>
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<refname>sd_bus_creds_get_augmented_mask</refname>
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<refname>sd_bus_creds_ref</refname>
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<refname>sd_bus_creds_unref</refname>
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<refname>sd_bus_creds_unrefp</refname>
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<refpurpose>Retrieve credentials object for the specified PID</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>sd_bus_creds_new_from_pid</function></funcdef>
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<paramdef>pid_t <parameter>pid</parameter></paramdef>
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<paramdef>uint64_t <parameter>creds_mask</parameter></paramdef>
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<paramdef>sd_bus_creds **<parameter>ret</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>uint64_t <function>sd_bus_creds_get_mask</function></funcdef>
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<paramdef>const sd_bus_creds *<parameter>c</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>uint64_t <function>sd_bus_creds_get_augmented_mask</function></funcdef>
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<paramdef>const sd_bus_creds *<parameter>c</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>sd_bus_creds *<function>sd_bus_creds_ref</function></funcdef>
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<paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>sd_bus_creds *<function>sd_bus_creds_unref</function></funcdef>
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<paramdef>sd_bus_creds *<parameter>c</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>void <function>sd_bus_creds_unrefp</function></funcdef>
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<paramdef>sd_bus_creds **<parameter>c</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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<para>
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<constant>SD_BUS_CREDS_PID</constant>,
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<constant>SD_BUS_CREDS_PPID</constant>,
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<constant>SD_BUS_CREDS_TID</constant>,
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<constant>SD_BUS_CREDS_UID</constant>,
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<constant>SD_BUS_CREDS_EUID</constant>,
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<constant>SD_BUS_CREDS_SUID</constant>,
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<constant>SD_BUS_CREDS_FSUID</constant>,
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<constant>SD_BUS_CREDS_GID</constant>,
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<constant>SD_BUS_CREDS_EGID</constant>,
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<constant>SD_BUS_CREDS_SGID</constant>,
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<constant>SD_BUS_CREDS_FSGID</constant>,
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<constant>SD_BUS_CREDS_SUPPLEMENTARY_GIDS</constant>,
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<constant>SD_BUS_CREDS_COMM</constant>,
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<constant>SD_BUS_CREDS_TID_COMM</constant>,
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<constant>SD_BUS_CREDS_EXE</constant>,
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<constant>SD_BUS_CREDS_CMDLINE</constant>,
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<constant>SD_BUS_CREDS_CGROUP</constant>,
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<constant>SD_BUS_CREDS_UNIT</constant>,
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<constant>SD_BUS_CREDS_SLICE</constant>,
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<constant>SD_BUS_CREDS_USER_UNIT</constant>,
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<constant>SD_BUS_CREDS_USER_SLICE</constant>,
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<constant>SD_BUS_CREDS_SESSION</constant>,
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<constant>SD_BUS_CREDS_OWNER_UID</constant>,
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<constant>SD_BUS_CREDS_EFFECTIVE_CAPS</constant>,
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<constant>SD_BUS_CREDS_PERMITTED_CAPS</constant>,
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<constant>SD_BUS_CREDS_INHERITABLE_CAPS</constant>,
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<constant>SD_BUS_CREDS_BOUNDING_CAPS</constant>,
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<constant>SD_BUS_CREDS_SELINUX_CONTEXT</constant>,
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<constant>SD_BUS_CREDS_AUDIT_SESSION_ID</constant>,
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<constant>SD_BUS_CREDS_AUDIT_LOGIN_UID</constant>,
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<constant>SD_BUS_CREDS_TTY</constant>,
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<constant>SD_BUS_CREDS_UNIQUE_NAME</constant>,
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<constant>SD_BUS_CREDS_WELL_KNOWN_NAMES</constant>,
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<constant>SD_BUS_CREDS_DESCRIPTION</constant>,
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<constant>SD_BUS_CREDS_AUGMENT</constant>,
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<constant>_SD_BUS_CREDS_ALL</constant>
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</para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>sd_bus_creds_new_from_pid()</function> creates a
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new credentials object and fills it with information about the
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process <parameter>pid</parameter>. The pointer to this object
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will be stored in the <parameter>ret</parameter> pointer. Note that
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credential objects may also be created and retrieved via
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<citerefentry><refentrytitle>sd_bus_get_name_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_get_owner_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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and
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<citerefentry><refentrytitle>sd_bus_message_get_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
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<para>The information that will be stored is determined by
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<parameter>creds_mask</parameter>. It may contain a subset of ORed
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constants <constant>SD_BUS_CREDS_PID</constant>,
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<constant>SD_BUS_CREDS_PPID</constant>,
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<constant>SD_BUS_CREDS_TID</constant>,
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<constant>SD_BUS_CREDS_UID</constant>,
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<constant>SD_BUS_CREDS_EUID</constant>,
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<constant>SD_BUS_CREDS_SUID</constant>,
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<constant>SD_BUS_CREDS_FSUID</constant>,
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<constant>SD_BUS_CREDS_GID</constant>,
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<constant>SD_BUS_CREDS_EGID</constant>,
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<constant>SD_BUS_CREDS_SGID</constant>,
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<constant>SD_BUS_CREDS_FSGID</constant>,
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<constant>SD_BUS_CREDS_SUPPLEMENTARY_GIDS</constant>,
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<constant>SD_BUS_CREDS_COMM</constant>,
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<constant>SD_BUS_CREDS_TID_COMM</constant>,
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<constant>SD_BUS_CREDS_EXE</constant>,
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<constant>SD_BUS_CREDS_CMDLINE</constant>,
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<constant>SD_BUS_CREDS_CGROUP</constant>,
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<constant>SD_BUS_CREDS_UNIT</constant>,
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<constant>SD_BUS_CREDS_SLICE</constant>,
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<constant>SD_BUS_CREDS_USER_UNIT</constant>,
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<constant>SD_BUS_CREDS_USER_SLICE</constant>,
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<constant>SD_BUS_CREDS_SESSION</constant>,
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<constant>SD_BUS_CREDS_OWNER_UID</constant>,
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<constant>SD_BUS_CREDS_EFFECTIVE_CAPS</constant>,
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<constant>SD_BUS_CREDS_PERMITTED_CAPS</constant>,
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<constant>SD_BUS_CREDS_INHERITABLE_CAPS</constant>,
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<constant>SD_BUS_CREDS_BOUNDING_CAPS</constant>,
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<constant>SD_BUS_CREDS_SELINUX_CONTEXT</constant>,
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<constant>SD_BUS_CREDS_AUDIT_SESSION_ID</constant>,
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<constant>SD_BUS_CREDS_AUDIT_LOGIN_UID</constant>,
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<constant>SD_BUS_CREDS_TTY</constant>,
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<constant>SD_BUS_CREDS_UNIQUE_NAME</constant>,
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<constant>SD_BUS_CREDS_WELL_KNOWN_NAMES</constant>, and
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<constant>SD_BUS_CREDS_DESCRIPTION</constant>. Use the special
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value <constant>_SD_BUS_CREDS_ALL</constant> to request all
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supported fields. The <constant>SD_BUS_CREDS_AUGMENT</constant>
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constant may not be ORed into the mask for invocations of
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<function>sd_bus_creds_new_from_pid()</function>.</para>
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<para>Fields can be retrieved from the credentials object using
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<citerefentry><refentrytitle>sd_bus_creds_get_pid</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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and other functions which correspond directly to the constants
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listed above.</para>
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<para>A mask of fields which were actually successfully retrieved
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can be retrieved with
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<function>sd_bus_creds_get_mask()</function>. If the credentials
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object was created with
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<function>sd_bus_creds_new_from_pid()</function>, this will be a
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subset of fields requested in <parameter>creds_mask</parameter>.
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</para>
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<para>Similar to <function>sd_bus_creds_get_mask()</function>, the
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function <function>sd_bus_creds_get_augmented_mask()</function>
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returns a bitmask of field constants. The mask indicates which
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credential fields have been retrieved in a non-atomic fashion. For
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credential objects created via
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<function>sd_bus_creds_new_from_pid()</function>, this mask will be
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identical to the mask returned by
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<function>sd_bus_creds_get_mask()</function>. However, for
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credential objects retrieved via
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<function>sd_bus_get_name_creds()</function>, this mask will be set
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for the credential fields that could not be determined atomically
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at peer connection time, and which were later added by reading
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augmenting credential data from
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<filename>/proc</filename>. Similarly, for credential objects
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retrieved via <function>sd_bus_get_owner_creds()</function>, the
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mask is set for the fields that could not be determined atomically
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at bus creation time, but have been augmented. Similarly, for
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credential objects retrieved via
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<function>sd_bus_message_get_creds()</function>, the mask is set
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for the fields that could not be determined atomically at message
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sending time, but have been augmented. The mask returned by
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<function>sd_bus_creds_get_augmented_mask()</function> is always a
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subset of (or identical to) the mask returned by
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<function>sd_bus_creds_get_mask()</function> for the same
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object. The latter call hence returns all credential fields
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available in the credential object, the former then marks the
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subset of those that have been augmented. Note that augmented
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fields are unsuitable for authorization decisions, as they may be
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retrieved at different times, thus being subject to races. Hence,
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augmented fields should be used exclusively for informational
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purposes.
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</para>
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<para><function>sd_bus_creds_ref()</function> creates a new
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reference to the credentials object <parameter>c</parameter>. This
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object will not be destroyed until
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<function>sd_bus_creds_unref()</function> has been called as many
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times plus once more. Once the reference count has dropped to zero,
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<parameter>c</parameter> cannot be used anymore, so further
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calls to <function>sd_bus_creds_ref(c)</function> or
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<function>sd_bus_creds_unref(c)</function> are illegal.</para>
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<para><function>sd_bus_creds_unref()</function> destroys a reference
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to <parameter>c</parameter>.</para>
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<para><function>sd_bus_creds_unrefp()</function> is similar to
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<function>sd_bus_creds_unref()</function> but takes a pointer to a
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pointer to an <type>sd_bus_creds</type> object. This call is useful in
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conjunction with GCC's and LLVM's <ulink
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url="https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html">Clean-up
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Variable Attribute</ulink>. Note that this function is defined as
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inline function.</para>
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<para><function>sd_bus_creds_ref()</function>,
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<function>sd_bus_creds_unref()</function> and
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<function>sd_bus_creds_unrefp()</function> execute no operation if
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the passed in bus credentials object is
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<constant>NULL</constant>.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>On success, <function>sd_bus_creds_new_from_pid()</function>
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returns 0 or a positive integer. On failure, it returns a negative
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errno-style error code.</para>
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<para><function>sd_bus_creds_get_mask()</function> returns the
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mask of successfully acquired fields.</para>
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<para><function>sd_bus_creds_get_augmented_mask()</function>
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returns the mask of fields that have been augmented from data in
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<filename>/proc</filename>, and are thus not suitable for
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authorization decisions.</para>
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<para><function>sd_bus_creds_ref()</function> always returns the
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argument.</para>
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<para><function>sd_bus_creds_unref()</function> always returns
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<constant>NULL</constant>.</para>
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</refsect1>
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<refsect1>
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<title>Reference ownership</title>
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<para>Function <function>sd_bus_creds_new_from_pid()</function>
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creates a new object and the caller owns the sole reference. When
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not needed anymore, this reference should be destroyed with
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<citerefentry><refentrytitle>sd_bus_creds_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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</para>
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</refsect1>
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<refsect1>
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<title>Errors</title>
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<para>Returned errors may indicate the following problems:</para>
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<variablelist>
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<varlistentry>
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<term><constant>-ESRCH</constant></term>
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<listitem><para>Specified <parameter>pid</parameter> could not
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be found.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-EINVAL</constant></term>
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<listitem><para>Specified parameter is invalid
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(<constant>NULL</constant> in case of output
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parameters).</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ENOMEM</constant></term>
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<listitem><para>Memory allocation failed.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-EOPNOTSUPP</constant></term>
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<listitem><para>One of the requested fields is unknown to the local system.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para><function>sd_bus_creds_new_from_pid()</function> and the
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other calls described here are available as a shared library,
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which can be compiled and linked to with the
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<constant>libsystemd</constant> <citerefentry
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project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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file.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_creds_get_pid</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_get_name_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_get_owner_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_bus_message_get_creds</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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