NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | ENVIRONMENT | SEE ALSO | COLOPHON

SD_WATCHDOG_ENABLED(3)       sd_watchdog_enabled      SD_WATCHDOG_ENABLED(3)

NAME         top

       sd_watchdog_enabled - Check whether the service manager expects
       watchdog keep-alive notifications from a service

SYNOPSIS         top

       #include <systemd/sd-daemon.h>

       int sd_watchdog_enabled(int unset_environment, uint64_t *usec);

DESCRIPTION         top

       sd_watchdog_enabled() may be called by a service to detect whether
       the service manager expects regular keep-alive watchdog notification
       events from it, and the timeout after which the manager will act on
       the service if it did not get such a notification.

       If the $WATCHDOG_USEC environment variable is set, and the
       $WATCHDOG_PID variable is unset or set to the PID of the current
       process, the service manager expects notifications from this process.
       The manager will usually terminate a service when it does not get a
       notification message within the specified time after startup and
       after each previous message. It is recommended that a daemon sends a
       keep-alive notification message to the service manager every half of
       the time returned here. Notification messages may be sent with
       sd_notify(3) with a message string of "WATCHDOG=1".

       If the unset_environment parameter is non-zero, sd_watchdog_enabled()
       will unset the $WATCHDOG_USEC and $WATCHDOG_PID environment variables
       before returning (regardless of whether the function call itself
       succeeded or not). Those variables are no longer inherited by child
       processes. Further calls to sd_watchdog_enabled() will also return
       with zero.

       If the usec parameter is non-NULL, sd_watchdog_enabled() will write
       the timeout in µs for the watchdog logic to it.

       To enable service supervision with the watchdog logic, use
       WatchdogSec= in service files. See systemd.service(5) for details.

       Use sd_event_set_watchdog(3) to enable automatic watchdog support in
       sd-event(3)-based event loops.

RETURN VALUE         top

       On failure, this call returns a negative errno-style error code. If
       the service manager expects watchdog keep-alive notification messages
       to be sent, > 0 is returned, otherwise 0 is returned. Only if the
       return value is > 0, the usec parameter is valid after the call.

NOTES         top

       These APIs are implemented as a shared library, which can be compiled
       and linked to with the libsystemd pkg-config(1) file.

       Internally, this functions parses the $WATCHDOG_PID and
       $WATCHDOG_USEC environment variable. The call will ignore these
       variables if $WATCHDOG_PID does not contain the PID of the current
       process, under the assumption that in that case, the variables were
       set for a different process further up the process tree.

ENVIRONMENT         top

       $WATCHDOG_PID
           Set by the system manager for supervised process for which
           watchdog support is enabled, and contains the PID of that
           process. See above for details.

       $WATCHDOG_USEC
           Set by the system manager for supervised process for which
           watchdog support is enabled, and contains the watchdog timeout in
           µs See above for details.

SEE ALSO         top

       systemd(1), sd-daemon(3), daemon(7), systemd.service(5),
       sd_notify(3), sd_event_set_watchdog(3)

COLOPHON         top

       This page is part of the systemd (systemd system and service manager)
       project.  Information about the project can be found at 
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have a bug
       report for this manual page, see 
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.  This
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       COLOPHON (which is not part of the original manual page), send a mail
       to man-pages@man7.org

systemd 231                                           SD_WATCHDOG_ENABLED(3)