Provided by: systemd_204-5ubuntu20.31_amd64 

NAME
sd_booted - Test whether the system is running the systemd init system
SYNOPSIS
#include <systemd/sd-daemon.h>
int sd_booted(void);
DESCRIPTION
sd_booted() checks whether the system was booted up using the systemd init system.
RETURN VALUE
On failure, this call returns a negative errno-style error code. If the system was booted up with systemd
as init system, this call returns a positive return value, zero otherwise.
NOTES
This function is provided by the reference implementation of APIs for new-style daemons and distributed
with the systemd package. The algorithm it implements is simple, and can easily be reimplemented in
daemons if it is important to support this interface without using the reference implementation.
Internally, this function checks whether the directory /run/systemd/system/ exists. A simple check like
this can also be implemented trivially in shell or any other language.
For details about the algorithm check the liberally licensed reference implementation sources:
http://cgit.freedesktop.org/systemd/systemd/plain/src/libsystemd-daemon/sd-daemon.c and
http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-daemon.h
sd_booted() is implemented in the reference implementation's sd-daemon.c and sd-daemon.h files. These
interfaces are available as shared library, which can be compiled and linked to with the
libsystemd-daemonpkg-config(1) file. Alternatively, applications consuming these APIs may copy the
implementation into their source tree. For more details about the reference implementation see sd-
daemon(3).
If the reference implementation is used as drop-in files and -DDISABLE_SYSTEMD is set during compilation
this function will always return 0 and otherwise become a NOP.
SEE ALSO
systemd(1), sd-daemon(3)
systemd 204 SD_BOOTED(3)