| <?xml version='1.0'?> <!--*-nxml-*--> |
| <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" |
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| Copyright 2012 Lennart Poettering |
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| |
| <refentry id="sd_journal_print"> |
| |
| <refentryinfo> |
| <title>sd_journal_print</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_journal_print</refentrytitle> |
| <manvolnum>3</manvolnum> |
| </refmeta> |
| |
| <refnamediv> |
| <refname>sd_journal_print</refname> |
| <refname>sd_journal_printv</refname> |
| <refname>sd_journal_send</refname> |
| <refname>sd_journal_sendv</refname> |
| <refname>sd_journal_perror</refname> |
| <refname>SD_JOURNAL_SUPPRESS_LOCATION</refname> |
| <refpurpose>Submit log entries to the journal</refpurpose> |
| </refnamediv> |
| |
| <refsynopsisdiv> |
| <funcsynopsis> |
| <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo> |
| |
| <funcprototype> |
| <funcdef>int <function>sd_journal_print</function></funcdef> |
| <paramdef>int <parameter>priority</parameter></paramdef> |
| <paramdef>const char* <parameter>format</parameter></paramdef> |
| <paramdef>...</paramdef> |
| </funcprototype> |
| |
| <funcprototype> |
| <funcdef>int <function>sd_journal_printv</function></funcdef> |
| <paramdef>int <parameter>priority</parameter></paramdef> |
| <paramdef>const char* <parameter>format</parameter></paramdef> |
| <paramdef>va_list <parameter>ap</parameter></paramdef> |
| </funcprototype> |
| |
| <funcprototype> |
| <funcdef>int <function>sd_journal_send</function></funcdef> |
| <paramdef>const char* <parameter>format</parameter></paramdef> |
| <paramdef>...</paramdef> |
| </funcprototype> |
| |
| <funcprototype> |
| <funcdef>int <function>sd_journal_sendv</function></funcdef> |
| <paramdef>const struct iovec *<parameter>iov</parameter></paramdef> |
| <paramdef>int <parameter>n</parameter></paramdef> |
| </funcprototype> |
| |
| <funcprototype> |
| <funcdef>int <function>sd_journal_perror</function></funcdef> |
| <paramdef>const char* <parameter>message</parameter></paramdef> |
| </funcprototype> |
| |
| </funcsynopsis> |
| </refsynopsisdiv> |
| |
| <refsect1> |
| <title>Description</title> |
| |
| <para><function>sd_journal_print()</function> may be |
| used to submit simple, plain text log entries to the |
| system journal. The first argument is a priority |
| value. This is followed by a format string and its |
| parameters, similar to |
| <citerefentry><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
| or |
| <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>. The |
| priority value is one of |
| <literal>LOG_EMERG</literal>, |
| <literal>LOG_ALERT</literal>, |
| <literal>LOG_CRIT</literal>, |
| <literal>LOG_ERR</literal>, |
| <literal>LOG_WARNING</literal>, |
| <literal>LOG_NOTICE</literal>, |
| <literal>LOG_INFO</literal>, |
| <literal>LOG_DEBUG</literal>, as defined in |
| <filename>syslog.h</filename>, see |
| <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
| for details. It is recommended to use this call to |
| submit log messages in the application locale or system |
| locale and in UTF-8 format, but no such restrictions |
| are enforced.</para> |
| |
| <para><function>sd_journal_printv()</function> is |
| similar to <function>sd_journal_print()</function> but |
| takes a variable argument list encapsulated in an |
| object of type <literal>va_list</literal> (see |
| <citerefentry><refentrytitle>stdarg</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
| for more information) instead of the format string. It |
| is otherwise equivalent in behavior.</para> |
| |
| <para><function>sd_journal_send()</function> may be |
| used to submit structured log entries to the system |
| journal. It takes a series of format strings, each |
| immediately followed by their associated parameters, |
| terminated by NULL. The strings passed should be of |
| the format <literal>VARIABLE=value</literal>. The |
| variable name must be in uppercase and consist only of |
| characters, numbers and underscores, and may not begin |
| with an underscore. (All assignments that do not |
| follow this syntax will be ignored.) The value can be |
| of any size and format. It is highly recommended to |
| submit text strings formatted in the UTF-8 character |
| encoding only, and submit binary fields only when |
| formatting in UTf-8 strings is not sensible. A number |
| of well known fields are defined, see |
| <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
| for details, but additional application defined fields |
| may be used. A variable may be assigned more than one |
| value per entry.</para> |
| |
| <para><function>sd_journal_sendv()</function> is |
| similar to <function>sd_journal_send()</function> but |
| takes an array of <literal>struct iovec</literal> (as |
| defined in <filename>uio.h</filename>, see |
| <citerefentry><refentrytitle>readv</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
| for details) instead of the format string. Each |
| structure should reference one field of the entry to |
| submit. The second argument specifies the number of |
| structures in the |
| array. <function>sd_journal_sendv()</function> is |
| particularly useful to submit binary objects to the |
| journal where that is necessary.</para> |
| |
| <para><function>sd_journal_perror()</function> is a |
| similar to |
| <citerefentry><refentrytitle>perror</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
| and writes a message to the journal that consists of |
| the passed string, suffixed with ": " and a human |
| readable representation of the current error code |
| stored in |
| <citerefentry><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If |
| the message string is passed as NULL or empty string |
| only the error string representation will be written, |
| prefixed with nothing. An additional journal field |
| ERRNO= is included in the entry containing the numeric |
| error code formatted as decimal string. The log |
| priority used is <literal>LOG_ERR</literal> (3).</para> |
| |
| <para>Note that <function>sd_journal_send()</function> |
| is a wrapper around |
| <function>sd_journal_sendv()</function> to make it |
| easier to use when only text strings shall be |
| submitted. Also, the following two calls are |
| mostly equivalent:</para> |
| |
| <programlisting>sd_journal_print(LOG_INFO, "Hello World, this is PID %lu!", (unsigned long) getpid()); |
| |
| sd_journal_send("MESSAGE=Hello World, this is PID %lu!", (unsigned long) getpid(), |
| "PRIORITY=%i", LOG_INFO, |
| NULL);</programlisting> |
| |
| <para>Note that these calls implicitly add fields for |
| the source file, function name and code line where |
| invoked. This is implemented with macros. If this is |
| not desired it can be turned off by defining |
| SD_JOURNAL_SUPPRESS_LOCATION before including |
| <filename>sd-journal.h</filename>.</para> |
| |
| <para><citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
| and and <function>sd_journal_print()</function> may |
| largely be used interchangeably |
| functionality-wise. However, note that log messages |
| logged via the former take a different path to the |
| journal server than the later, and hence global |
| chronological ordering between the two streams cannot |
| be guaranteed. Using |
| <function>sd_journal_print()</function> has the |
| benefit of logging source code line, file names, and |
| functions as meta data along all entries, and |
| guaranteeing chronological ordering with structured |
| log entries that are generated via |
| <function>sd_journal_send()</function>. Using |
| <function>syslog()</function> has the benefit of being |
| more portable.</para> |
| </refsect1> |
| |
| <refsect1> |
| <title>Return Value</title> |
| |
| <para>The four calls return 0 on success or a negative |
| errno-style error code. The |
| <citerefentry><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
| variable itself is not altered.</para> |
| </refsect1> |
| |
| <refsect1> |
| <title>Notes</title> |
| |
| <para>The <function>sd_journal_print()</function>, |
| <function>sd_journal_printv()</function>, |
| <function>sd_journal_send()</function> and |
| <function>sd_journal_sendv()</function> interfaces |
| are available as shared library, which can be compiled |
| and linked to with the |
| <literal>libsystemd-journal</literal> |
| <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry> |
| file.</para> |
| </refsect1> |
| |
| <refsect1> |
| <title>See Also</title> |
| |
| <para> |
| <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>sd_journal_stream_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>perror</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
| <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry> |
| </para> |
| </refsect1> |
| |
| </refentry> |