summaryrefslogtreecommitdiff
path: root/man/sd_is_fifo.xml
blob: a790c370e10652b8cf5c909ba36f8093b7980d98 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
<?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">

<!--
  This file is part of systemd.

  Copyright 2010 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->

<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 <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 (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
                <constant>NULL</constant>, 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>