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Diffstat (limited to 'src/libsystemd/sd_journal_print.xml')
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diff --git a/src/libsystemd/sd_journal_print.xml b/src/libsystemd/sd_journal_print.xml new file mode 100644 index 0000000000..2d8dd635aa --- /dev/null +++ b/src/libsystemd/sd_journal_print.xml @@ -0,0 +1,246 @@ +<?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 2012 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_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 project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry> or + <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>. + The priority value is one of <constant>LOG_EMERG</constant>, <constant>LOG_ALERT</constant>, + <constant>LOG_CRIT</constant>, <constant>LOG_ERR</constant>, <constant>LOG_WARNING</constant>, + <constant>LOG_NOTICE</constant>, <constant>LOG_INFO</constant>, <constant>LOG_DEBUG</constant>, as defined in + <filename>syslog.h</filename>, see <citerefentry + project='man-pages'><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. Note that log messages written using this function are generally not + expected to end in a new-line character. However, as all trailing whitespace (including spaces, new-lines, + tabulators and carriage returns) are automatically stripped from the logged string, it is acceptable to specify one + (or more). Empty lines (after trailing whitespace removal) are suppressed. On non-empty lines, leading whitespace + (as well as inner whitespace) is left unmodified. </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 + <varname>va_list</varname> (see + <citerefentry project='man-pages'><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 + <constant>NULL</constant>. 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. If this function is used, trailing whitespace is automatically removed from each formatted field.</para> + + <para><function>sd_journal_sendv()</function> is similar to <function>sd_journal_send()</function> but takes an + array of <varname>struct iovec</varname> (as defined in <filename>uio.h</filename>, see <citerefentry + project='man-pages'><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. Note that this function wil not strip trailing + whitespace of the passed fields, but passes the specified data along unmodified. This is different from both + <function>sd_journal_print()</function> and <function>sd_journal_send()</function> described above, which are based + on format strings, and do strip trailing whitespace.</para> + + <para><function>sd_journal_perror()</function> is a similar to + <citerefentry project='die-net'><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 project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>. + If the message string is passed as <constant>NULL</constant> 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 + <constant>LOG_ERR</constant> (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 project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry> + 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, filenames, and + functions as metadata 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 project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry> + variable itself is not altered.</para> + + <para>If + <citerefentry><refentrytitle>systemd-journald</refentrytitle><manvolnum>8</manvolnum></citerefentry> + is not running (the socket is not present), those functions do + nothing, and also return 0.</para> + </refsect1> + + <refsect1> + <title>Thread safety</title> + <para>All functions listed here are thread-safe and may be called in parallel from multiple threads.</para> + + <para><function>sd_journal_sendv()</function> is "async signal safe" in the meaning of + <citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>. + </para> + + <para><function>sd_journal_print</function>, + <function>sd_journal_printv</function>, + <function>sd_journal_send</function>, and + <function>sd_journal_perror</function> are + not async signal safe.</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 a shared library, which can be compiled and linked to with the + <constant>libsystemd</constant> <citerefentry project='die-net'><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 project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry project='die-net'><refentrytitle>perror</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>, + <citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>, + <citerefentry project='man-pages'><refentrytitle>socket</refentrytitle><manvolnum>7</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |