Hi,

This does work on both Raspberry Pi OS (on RPi4) and Linux Mint (on x86_64):

#include <Core/Core.h>

using namespace Upp;

String LoadFileRaw(const char *filename){
	int fd = open(filename,O_RDONLY);
	if(fd!=-1){
		char buf[4096];
		StringBuffer s;
		int len;
		while((len=read(fd,buf,4096))==4096) s.Cat(buf,len);
		if(len>0) s.Cat(buf,len);
		close(fd);
		if(s.GetCount()>0) return s;
	}
	return String::GetVoid();
}

CONSOLE_APP_MAIN
{
	String meminfo = LoadFileRaw("/proc/meminfo");
	Cout() << meminfo << "\n\n";
}

Also:

LoadFileRaw("/sys/devices/virtual/thermal/thermal_zone0/temp");

works fine on RPi4.

Best regards,

Tom