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NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |NOTES |ENVIRONMENT |HISTORY |SEE ALSO |COLOPHON | |
SD_WATCHDOG_ENABLED(3) sd_watchdog_enabledSD_WATCHDOG_ENABLED(3)sd_watchdog_enabled - Check whether the service manager expects watchdog keep-alive notifications from a service
#include <systemd/sd-daemon.h>int sd_watchdog_enabled(intunset_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$WATCHDOG_USEC environment variable is set, and the$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 withsd_notify(3) with a message string of "WATCHDOG=1". If theunset_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 tosd_watchdog_enabled()will also return with zero. If theusec 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, useWatchdogSec= in service files. Seesystemd.service(5) for details. Usesd_event_set_watchdog(3) to enable automatic watchdog support insd-event(3)-based event loops.
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, theusec parameter is valid after the call.
Functions described here are available as a shared library, which can be compiled against and linked to with thelibsystemd pkg-config(1) file. The code described here usesgetenv(3), which is declared to be not multi-thread-safe. This means that the code calling the functions described here must not callsetenv(3) from a parallel thread. It is recommended to only do calls tosetenv()from an early phase of the program when no other threads have been started. Internally, this function 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.
$WATCHDOG_PID Set by the system manager for supervised process for which watchdog support is enabled, and contains the PID of that process. See above for details. Added in version 209.$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. Added in version 209.
sd_watchdog_enabled()was added in version 209.
systemd(1),sd-daemon(3),daemon(7),systemd.service(5),sd_notify(3),sd_event_set_watchdog(3)
This page is part of thesystemd (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 page was obtained from the project's upstream Git repository ⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11. (At that time, the date of the most recent commit that was found in the repository was 2025-08-11.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which isnot part of the original manual page), send a mail to man-pages@man7.orgsystemd 258~rc2SD_WATCHDOG_ENABLED(3)Pages that refer to this page:sd-daemon(3), sd_event_set_watchdog(3), sd_notify(3), systemd.exec(5), systemd.service(5), systemd.directives(7), systemd.index(7)
HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |