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Diffstat (limited to 'man/systemd.exec.xml')
| -rw-r--r-- | man/systemd.exec.xml | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/man/systemd.exec.xml b/man/systemd.exec.xml index a39e800854..dbfc7692f7 100644 --- a/man/systemd.exec.xml +++ b/man/systemd.exec.xml @@ -1539,6 +1539,26 @@ <citerefentry project='man-pages'><refentrytitle>termcap</refentrytitle><manvolnum>5</manvolnum></citerefentry>. </para></listitem> </varlistentry> + + <varlistentry> + <term><varname>$JOURNAL_STREAM</varname></term> + + <listitem><para>If the standard output or standard error output of the executed processes are connected to the + journal (for example, by setting <varname>StandardError=journal</varname>) <varname>$JOURNAL_STREAM</varname> + contains the device and inode numbers of the connection file descriptor, formatted in decimal, separated by a + colon (<literal>:</literal>). This permits invoked processes to safely detect whether their standard output or + standard error output are connected to the journal. The device and inode numbers of the file descriptors should + be compared with the values set in the environment variable to determine whether the process output is still + connected to the journal. Note that it is generally not sufficient to only check whether + <varname>$JOURNAL_STREAM</varname> is set at all as services might invoke external processes replacing their + standard output or standard error output, without unsetting the environment variable.</para> + + <para>This environment variable is primarily useful to allow services to optionally upgrade their used log + protocol to the native journal protocol (using + <citerefentry><refentrytitle>sd_journal_print</refentrytitle><manvolnum>3</manvolnum></citerefentry> and other + functions) if their standard output or standard error output is connected to the journal anyway, thus enabling + delivery of structured metadata along with logged messages.</para></listitem> + </varlistentry> </variablelist> <para>Additional variables may be configured by the following |