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<refentry id="sd_journal_query_unique">
- <refentryinfo>
- <title>sd_journal_query_unique</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_query_unique</refentrytitle>
- <manvolnum>3</manvolnum>
- </refmeta>
-
- <refnamediv>
- <refname>sd_journal_query_unique</refname>
- <refname>sd_journal_enumerate_unique</refname>
- <refname>sd_journal_restart_unique</refname>
- <refname>SD_JOURNAL_FOREACH_UNIQUE</refname>
- <refpurpose>Read unique data fields from the journal</refpurpose>
- </refnamediv>
-
- <refsynopsisdiv>
- <funcsynopsis>
- <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
-
- <funcprototype>
- <funcdef>int <function>sd_journal_query_unique</function></funcdef>
- <paramdef>sd_journal* <parameter>j</parameter></paramdef>
- <paramdef>const char* <parameter>field</parameter></paramdef>
- </funcprototype>
-
- <funcprototype>
- <funcdef>int <function>sd_journal_enumerate_unique</function></funcdef>
- <paramdef>sd_journal* <parameter>j</parameter></paramdef>
- <paramdef>const void** <parameter>data</parameter></paramdef>
- <paramdef>size_t* <parameter>length</parameter></paramdef>
- </funcprototype>
-
- <funcprototype>
- <funcdef>void <function>sd_journal_restart_unique</function></funcdef>
- <paramdef>sd_journal* <parameter>j</parameter></paramdef>
- </funcprototype>
-
- <funcprototype>
- <funcdef><function>SD_JOURNAL_FOREACH_UNIQUE</function></funcdef>
- <paramdef>sd_journal* <parameter>j</parameter></paramdef>
- <paramdef>const void* <parameter>data</parameter></paramdef>
- <paramdef>size_t <parameter>length</parameter></paramdef>
- </funcprototype>
-
- </funcsynopsis>
- </refsynopsisdiv>
-
- <refsect1>
- <title>Description</title>
-
- <para><function>sd_journal_query_unique()</function>
- queries the journal for all unique values the
- specified field can take. It takes two arguments: the
- journal to query and the field name to look
- for. Well-known field names are listed on
- <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>. Field
- names must be specified without a trailing '='. After
- this function has been executed successfully the field
- values may be queried using
- <function>sd_journal_enumerate_unique()</function>. Invoking
- this call a second time will change the field name
- being queried and reset the enumeration index to the
- first field value that matches.</para>
-
- <para><function>sd_journal_enumerate_unique()</function>
- may be used to iterate through all data fields which
- match the previously selected field name as set with
- <function>sd_journal_query_unique()</function>. On
- each invocation the next field data matching the field
- name is returned. The order of the returned data
- fields is not defined. It takes three arguments: the
- journal context object, plus a pair of pointers to
- pointer/size variables where the data object and its
- size shall be stored in. The returned data is in a
- read-only memory map and is only valid until the next
- invocation of
- <function>sd_journal_enumerate_unique()</function>. Note
- that the data returned will be prefixed with the field
- name and '='. Note that this call is subject to the
- data field size threshold as controlled by
- <function>sd_journal_set_data_threshold()</function>.</para>
-
- <para><function>sd_journal_restart_unique()</function>
- resets the data enumeration index to the beginning of
- the list. The next invocation of
- <function>sd_journal_enumerate_unique()</function>
- will return the first field data matching the field
- name again.</para>
-
- <para>Note that the
- <function>SD_JOURNAL_FOREACH_UNIQUE()</function> macro
- may be used as a handy wrapper around
- <function>sd_journal_restart_unique()</function> and
- <function>sd_journal_enumerate_unique()</function>.</para>
-
- <para>Note that these functions currently are not
- influenced by matches set with
- <function>sd_journal_add_match()</function> but this
- might change in a later version of this
- software.</para>
- </refsect1>
-
- <refsect1>
- <title>Return Value</title>
-
- <para><function>sd_journal_query_unique()</function>
- returns 0 on success or a negative errno-style error
- code. <function>sd_journal_enumerate_unique()</function>
- returns a positive integer if the next field data has
- been read, 0 when no more fields are known, or a
- negative errno-style error
- code. <function>sd_journal_restart_unique()</function>
- returns nothing.</para>
- </refsect1>
-
- <refsect1>
- <title>Notes</title>
-
- <para>The <function>sd_journal_query_unique()</function>,
- <function>sd_journal_enumerate_unique()</function> and
- <function>sd_journal_restart_unique()</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>Examples</title>
-
- <para>Use the
- <function>SD_JOURNAL_FOREACH_UNIQUE</function> macro
- to iterate through all values a field of the journal
- can take. The following example lists all unit names
- referenced in the journal:</para>
-
- <programlisting>#include <stdio.h>
+ <refentryinfo>
+ <title>sd_journal_query_unique</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_query_unique</refentrytitle>
+ <manvolnum>3</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>sd_journal_query_unique</refname>
+ <refname>sd_journal_enumerate_unique</refname>
+ <refname>sd_journal_restart_unique</refname>
+ <refname>SD_JOURNAL_FOREACH_UNIQUE</refname>
+ <refpurpose>Read unique data fields from the journal</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
+
+ <funcprototype>
+ <funcdef>int <function>sd_journal_query_unique</function></funcdef>
+ <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+ <paramdef>const char *<parameter>field</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>int <function>sd_journal_enumerate_unique</function></funcdef>
+ <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+ <paramdef>const void **<parameter>data</parameter></paramdef>
+ <paramdef>size_t *<parameter>length</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef>void <function>sd_journal_restart_unique</function></funcdef>
+ <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+ </funcprototype>
+
+ <funcprototype>
+ <funcdef><function>SD_JOURNAL_FOREACH_UNIQUE</function></funcdef>
+ <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+ <paramdef>const void *<parameter>data</parameter></paramdef>
+ <paramdef>size_t <parameter>length</parameter></paramdef>
+ </funcprototype>
+
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para><function>sd_journal_query_unique()</function> queries the
+ journal for all unique values the specified field can take. It
+ takes two arguments: the journal to query and the field name to
+ look for. Well-known field names are listed on
+ <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
+ Field names must be specified without a trailing '='. After this
+ function has been executed successfully the field values may be
+ queried using <function>sd_journal_enumerate_unique()</function>.
+ Invoking this call a second time will change the field name being
+ queried and reset the enumeration index to the first field value
+ that matches.</para>
+
+ <para><function>sd_journal_enumerate_unique()</function> may be
+ used to iterate through all data fields which match the previously
+ selected field name as set with
+ <function>sd_journal_query_unique()</function>. On each invocation
+ the next field data matching the field name is returned. The order
+ of the returned data fields is not defined. It takes three
+ arguments: the journal context object, plus a pair of pointers to
+ pointer/size variables where the data object and its size shall be
+ stored in. The returned data is in a read-only memory map and is
+ only valid until the next invocation of
+ <function>sd_journal_enumerate_unique()</function>. Note that the
+ data returned will be prefixed with the field name and '='. Note
+ that this call is subject to the data field size threshold as
+ controlled by
+ <function>sd_journal_set_data_threshold()</function>.</para>
+
+ <para><function>sd_journal_restart_unique()</function> resets the
+ data enumeration index to the beginning of the list. The next
+ invocation of <function>sd_journal_enumerate_unique()</function>
+ will return the first field data matching the field name
+ again.</para>
+
+ <para>Note that the
+ <function>SD_JOURNAL_FOREACH_UNIQUE()</function> macro may be used
+ as a handy wrapper around
+ <function>sd_journal_restart_unique()</function> and
+ <function>sd_journal_enumerate_unique()</function>.</para>
+
+ <para>Note that these functions currently are not influenced by
+ matches set with <function>sd_journal_add_match()</function> but
+ this might change in a later version of this software.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Return Value</title>
+
+ <para><function>sd_journal_query_unique()</function> returns 0 on
+ success or a negative errno-style error code.
+ <function>sd_journal_enumerate_unique()</function> returns a
+ positive integer if the next field data has been read, 0 when no
+ more fields are known, or a negative errno-style error code.
+ <function>sd_journal_restart_unique()</function> returns
+ nothing.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Notes</title>
+
+ <para>The <function>sd_journal_query_unique()</function>,
+ <function>sd_journal_enumerate_unique()</function> and
+ <function>sd_journal_restart_unique()</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>Examples</title>
+
+ <para>Use the <function>SD_JOURNAL_FOREACH_UNIQUE</function> macro
+ to iterate through all values a field of the journal can take. The
+ following example lists all unit names referenced in the
+ journal:</para>
+
+ <programlisting>#include <stdio.h>
#include <string.h>
#include <systemd/sd-journal.h>
int main(int argc, char *argv[]) {
- sd_journal *j;
- const void *d;
- size_t l;
- int r;
-
- r = sd_journal_open(&j, SD_JOURNAL_LOCAL_ONLY);
- if (r < 0) {
- fprintf(stderr, "Failed to open journal: %s\n", strerror(-r));
- return 1;
- }
- r = sd_journal_query_unique(j, "_SYSTEMD_UNIT");
- if (r < 0) {
- fprintf(stderr, "Failed to query journal: %s\n", strerror(-r));
- return 1;
- }
- SD_JOURNAL_FOREACH_UNIQUE(j, d, l)
- printf("%.*s\n", (int) l, (const char*) d);
- sd_journal_close(j);
- return 0;
+ sd_journal *j;
+ const void *d;
+ size_t l;
+ int r;
+
+ r = sd_journal_open(&j, SD_JOURNAL_LOCAL_ONLY);
+ if (r < 0) {
+ fprintf(stderr, "Failed to open journal: %s\n", strerror(-r));
+ return 1;
+ }
+ r = sd_journal_query_unique(j, "_SYSTEMD_UNIT");
+ if (r < 0) {
+ fprintf(stderr, "Failed to query journal: %s\n", strerror(-r));
+ return 1;
+ }
+ SD_JOURNAL_FOREACH_UNIQUE(j, d, l)
+ printf("%.*s\n", (int) l, (const char*) d);
+ sd_journal_close(j);
+ return 0;
}</programlisting>
- </refsect1>
+ </refsect1>
- <refsect1>
- <title>See Also</title>
+ <refsect1>
+ <title>See Also</title>
- <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_journal_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- </para>
- </refsect1>
+ <para>
+ <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>sd_journal_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ </para>
+ </refsect1>
</refentry>
~ianmdlvl / elogind.git / blobdiff