find out true (according to xrandr) monitor DPI

xrandr --query | sed -n 's@\([A-Z0-1-]*\).* \(.*\)x\(.*\)+.*+.* \([0-9]\+\)mm x \([0-9]\+\)mm@"\1: ";(\2/\4+\3/\5)*12.7@p;'|bc -l
see summary. if you want to set dpi right away try this: xrandr --query | sed -n 's@\([A-Z0-1-]*\).* \(.*\)x\(.*\)+.*+.* \([0-9]\+\)mm x \([0-9]\+\)mm@"--output \1 --dpi ";(\2/\4+\3/\5)*12.7@p;'|bc -l|xargs -L1 xrandr all syntax should be POSIX compliant.
Sample Output
LVDS-1: 100.96760151825521147108
HDMI-1: 92.60728755320785681297

0
2017-06-23 03:44:40

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