( preceding discussion snipped...)

>> marc@quixote:/usr/local/harbour/harbour-3.0.0$ marc@quixote:/$ sudo find -name sysctl.h
>> ./usr/include/diet/sys/sysctl.h
>> ./usr/include/linux/sysctl.h
> As for that latter linux/sysctl.h, it seems that sysctl() was removed
> in Linux 5.5 and glibc 2.32. Perhaps you have more success on a
> somewhat older Devuan version such as chimaera? Or check for issues
> and hints from wherever you got the harbour source.
>
> Seehttps://www.man7.org/linux/man-pages/man2/sysctl.2.html for notes on
> the sysctl() removal from the kernel and glibc.

I have it on a fairly plain-vanilla daedalus installation:

> 544]cat /etc/os-release
> PRETTY_NAME="Devuan GNU/Linux 5 (daedalus)"
> NAME="Devuan GNU/Linux"
> VERSION_ID="5"
> VERSION="5 (daedalus)"
> VERSION_CODENAME="daedalus"
> ID=devuan
> ID_LIKE=debian
> HOME_URL="https://www.devuan.org/"
> SUPPORT_URL="https://devuan.org/os/community"
> BUG_REPORT_URL="https://bugs.devuan.org/"
> (base) 2023-10-16, 12:44 bobmon@montpad:~
> 545]find /usr -name sysctl.h
> find: ‘/usr/share/polkit-1/rules.d’: Permission denied
> /usr/src/linux-headers-6.1.0-13-common/include/uapi/linux/sysctl.h
> /usr/src/linux-headers-6.1.0-13-common/include/linux/sysctl.h
> /usr/src/linux-headers-6.1.0-13-common/include/linux/sched/sysctl.h
> /usr/src/linux-headers-6.1.0-12-common/include/uapi/linux/sysctl.h
> /usr/src/linux-headers-6.1.0-12-common/include/linux/sysctl.h
> /usr/src/linux-headers-6.1.0-12-common/include/linux/sched/sysctl.h
> /usr/include/linux/sysctl.h
> (base) 2023-10-16, 12:44 bobmon@montpad:~