sd-journal: introduce has_runtime_files and has_persistent_files

Also introduce sd_journal_has_runtime_files() and
sd_journal_has_persistent_files() to the public API. These functions
can be used to easily find out if the open journal files are runtime
and/or persistent.

6 files changed, 131 insertions, 2 deletions

diff --git a/Makefile-man.am b/Makefile-man.am
index 0055746a70..12900daa96 100644
--- a/Makefile-man.am
+++ b/Makefile-man.am
@@ -79,6 +79,7 @@ MANPAGES += \
 	man/sd_journal_get_fd.3 \
 	man/sd_journal_get_realtime_usec.3 \
 	man/sd_journal_get_usage.3 \
+	man/sd_journal_has_runtime_files.3 \
 	man/sd_journal_next.3 \
 	man/sd_journal_open.3 \
 	man/sd_journal_print.3 \
@@ -384,6 +385,7 @@ MANPAGES_ALIAS += \
 	man/sd_journal_get_events.3 \
 	man/sd_journal_get_monotonic_usec.3 \
 	man/sd_journal_get_timeout.3 \
+	man/sd_journal_has_persistent_files.3 \
 	man/sd_journal_next_skip.3 \
 	man/sd_journal_open_container.3 \
 	man/sd_journal_open_directory.3 \
@@ -711,6 +713,7 @@ man/sd_journal_get_data_threshold.3: man/sd_journal_get_data.3
 man/sd_journal_get_events.3: man/sd_journal_get_fd.3
 man/sd_journal_get_monotonic_usec.3: man/sd_journal_get_realtime_usec.3
 man/sd_journal_get_timeout.3: man/sd_journal_get_fd.3
+man/sd_journal_has_persistent_files.3: man/sd_journal_has_runtime_files.3
 man/sd_journal_next_skip.3: man/sd_journal_next.3
 man/sd_journal_open_container.3: man/sd_journal_open.3
 man/sd_journal_open_directory.3: man/sd_journal_open.3
@@ -1458,6 +1461,9 @@ man/sd_journal_get_monotonic_usec.html: man/sd_journal_get_realtime_usec.html
 man/sd_journal_get_timeout.html: man/sd_journal_get_fd.html
 	$(html-alias)
 
+man/sd_journal_has_persistent_files.html: man/sd_journal_has_runtime_files.html
+	$(html-alias)
+
 man/sd_journal_next_skip.html: man/sd_journal_next.html
 	$(html-alias)
 
@@ -2535,6 +2541,7 @@ EXTRA_DIST += \
 	man/sd_journal_get_fd.xml \
 	man/sd_journal_get_realtime_usec.xml \
 	man/sd_journal_get_usage.xml \
+	man/sd_journal_has_runtime_files.xml \
 	man/sd_journal_next.xml \
 	man/sd_journal_open.xml \
 	man/sd_journal_print.xml \
diff --git a/man/sd-journal.xml b/man/sd-journal.xml
index 9b1a52207f..a1185d372b 100644
--- a/man/sd-journal.xml
+++ b/man/sd-journal.xml
@@ -81,9 +81,11 @@
     <citerefentry><refentrytitle>sd_journal_get_cutoff_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
     <citerefentry><refentrytitle>sd_journal_get_cutoff_monotonic_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
     <citerefentry><refentrytitle>sd_journal_get_usage</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
-    <citerefentry><refentrytitle>sd_journal_get_catalog</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    <citerefentry><refentrytitle>sd_journal_get_catalog</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd_journal_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd_journal_has_runtime_files</refentrytitle><manvolnum>3</manvolnum></citerefentry>
     and
-    <citerefentry><refentrytitle>sd_journal_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    <citerefentry><refentrytitle>sd_journal_has_persistent_files</refentrytitle><manvolnum>3</manvolnum></citerefentry>
     for more information about the functions implemented.</para>
 
     <para>Command line access for submitting entries to the journal is
@@ -116,6 +118,8 @@
       <citerefentry><refentrytitle>sd_journal_get_fd</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>sd_journal_query_unique</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>sd_journal_get_catalog</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_journal_has_runtime_files</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_journal_has_persistent_files</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
       <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
diff --git a/man/sd_journal_has_runtime_files.xml b/man/sd_journal_has_runtime_files.xml
new file mode 100644
index 0000000000..237e649206
--- /dev/null
+++ b/man/sd_journal_has_runtime_files.xml
@@ -0,0 +1,95 @@
+<?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 2016 Jan Synáček
+
+  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_has_runtime_files">
+
+  <refentryinfo>
+    <title>sd_journal_has_runtime_files</title>
+    <productname>systemd</productname>
+
+    <authorgroup>
+      <author>
+        <contrib>Developer</contrib>
+        <firstname>Jan</firstname>
+        <surname>Synáček</surname>
+        <email>jan.synacek@gmail.com</email>
+      </author>
+    </authorgroup>
+  </refentryinfo>
+
+  <refmeta>
+    <refentrytitle>sd_journal_has_runtime_files</refentrytitle>
+    <manvolnum>3</manvolnum>
+  </refmeta>
+
+  <refnamediv>
+    <refname>sd_journal_has_runtime_files</refname>
+    <refname>sd_journal_has_persistent_files</refname>
+    <refpurpose>Query availability of runtime or persistent journal files.</refpurpose>
+  </refnamediv>
+
+  <refsynopsisdiv>
+    <funcsynopsis>
+      <funcsynopsisinfo>#include &lt;systemd/sd-journal.h&gt;</funcsynopsisinfo>
+
+      <funcprototype>
+        <funcdef>int <function>sd_journal_has_runtime_files</function></funcdef>
+        <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_journal_has_persistent_files</function></funcdef>
+        <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+      </funcprototype>
+
+    </funcsynopsis>
+  </refsynopsisdiv>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para><function>sd_journal_has_runtime_files()</function> returns a positive value
+    if runtime journal files (present in /run/systemd/journal/) have been found.
+    Otherwise returns 0.</para>
+
+    <para><function>sd_journal_has_persistent_files()</function> returns a positive value
+    if persistent journal files (present in /var/log/journal/) have been found.
+    Otherwise returns 0.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>Return value</title>
+    <para>Both <function>sd_journal_has_runtime_files()</function>
+    and <function>sd_journal_has_persistent_files()</function> return -EINVAL
+    if their argument is NULL.
+    </para>
+  </refsect1>
+
+  <refsect1>
+    <title>See Also</title>
+    <para>
+      <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    </para>
+  </refsect1>
+
+</refentry>
diff --git a/src/journal/journal-internal.h b/src/journal/journal-internal.h
index 9ff4fea7fb..fa5ca11636 100644
--- a/src/journal/journal-internal.h
+++ b/src/journal/journal-internal.h
@@ -115,6 +115,8 @@ struct sd_journal {
                                   removed, and there were no more
                                   files, so sd_j_enumerate_unique
                                   will return a value equal to 0. */
+        bool has_runtime_files:1;
+        bool has_persistent_files:1;
 
         size_t data_threshold;
 
diff --git a/src/journal/sd-journal.c b/src/journal/sd-journal.c
index cd5160154a..74a5e262f8 100644
--- a/src/journal/sd-journal.c
+++ b/src/journal/sd-journal.c
@@ -1292,6 +1292,12 @@ static int add_file(sd_journal *j, const char *prefix, const char *filename) {
                 return 0;
 
         path = strjoina(prefix, "/", filename);
+
+        if (!j->has_runtime_files && path_startswith(path, "/run/log/journal"))
+                j->has_runtime_files = true;
+        else if (!j->has_persistent_files && path_startswith(path, "/var/log/journal"))
+                j->has_persistent_files = true;
+
         return add_any_file(j, path);
 }
 
@@ -2630,3 +2636,15 @@ _public_ int sd_journal_get_data_threshold(sd_journal *j, size_t *sz) {
         *sz = j->data_threshold;
         return 0;
 }
+
+_public_ int sd_journal_has_runtime_files(sd_journal *j) {
+        assert_return(j, -EINVAL);
+
+        return j->has_runtime_files;
+}
+
+_public_ int sd_journal_has_persistent_files(sd_journal *j) {
+        assert_return(j, -EINVAL);
+
+        return j->has_persistent_files;
+}
diff --git a/src/systemd/sd-journal.h b/src/systemd/sd-journal.h
index 33e36149e9..7f16c69ce5 100644
--- a/src/systemd/sd-journal.h
+++ b/src/systemd/sd-journal.h
@@ -139,6 +139,9 @@ int sd_journal_reliable_fd(sd_journal *j);
 int sd_journal_get_catalog(sd_journal *j, char **text);
 int sd_journal_get_catalog_for_message_id(sd_id128_t id, char **text);
 
+int sd_journal_has_runtime_files(sd_journal *j);
+int sd_journal_has_persistent_files(sd_journal *j);
+
 /* the inverse condition avoids ambiguity of danling 'else' after the macro */
 #define SD_JOURNAL_FOREACH(j)                                           \
         if (sd_journal_seek_head(j) < 0) { }                            \