Skip to content
MoreDisplays

Type to search.
Manual contents

mdctl displays

Print the displays the machine is showing.

mdctl displays

What it prints

One display per line, left to right across the desk: reference, size, refresh rate, name, and [main] on the one carrying the menu bar.

What the machine is showing right now, left to right across the desk. Not what a group says it should be showing: this is the live topology.

mdctl displays
virtual:4C2E9A31-7F0B-4E58-9C1D-8A0F2B6D5E77   5120x1440 @ 60Hz  Home ultrawide  [main]
physical:A1B2C3D4-5E6F-4071-8293-A4B5C6D7E8F9  3840x2160 (7680x4320 px) @ 60Hz  Studio Display

The reference column comes first because the next command needs it

Everything else on the line is for recognising the display; the reference is what you paste into edid or protect. It is the same spelling the configuration file uses, so a display you can see here is one you can find in the file.

A display the app created is named through its own spec rather than through the ColorSync UUID CoreGraphics hands out for every display, ours included. Two spellings of one reference, with the tool printing the one you could not use, was a real bug.

Points and pixels

The size is in points, and the pixel size follows in brackets only when the two differ. On an ordinary display printing both would be noise; on a HiDPI display the difference is the whole point.

mdctl displays | wc -l
       2

Exit codes

The same four across every command, so a script can branch on the number without knowing which command produced it.

Code Name When
0 ok The command succeeded.
1 commandFailed The app understood the command and refused or failed it. The reason is on stderr.
2 usage The arguments were wrong. Nothing was sent.
3 appNotRunning No app is listening on the socket.