Check whether the service manager expects watchdog keep-alive notifications from a service
int sd_watchdog_enabled(int unset_environment, uint64_t *usec);
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 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). Further calls to sd_watchdog_enabled() will then return with zero, but the variable is no longer inherited by child processes.
If the usec parameter is non-NULL, sd_watchdog_enabled() will return the timeout in µs for the watchdog logic. The service manager will usually terminate a service when it did 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".
To enable service supervision with the watchdog logic, use WatchdogSec= in service files. See systemd.service(5) for details.
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.
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 containe 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.
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.
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.