How to detect availability of GUI in Bash/Shell?

Question

I'm writing a CLI in NodeJS. As I can easily run bash/shell commands using the child_process, I'd like to know the easiest most cross platform way to detect GUI availability in bash/shell.

Thanks!

Answer 1

On macOS, there's not a clearly appropriate way to check this from a shell, as such. There's a programmatic way, and we can use an interpreted language to take advantage of that.

Here's a little script that outputs one of three states, Mac GUI, Mac non-GUI, or X11:

#!/bin/bash

check_macos_gui() {
  command -v swift >/dev/null && swift <(cat <<"EOF"
import Security
var attrs = SessionAttributeBits(rawValue:0)
let result = SessionGetInfo(callerSecuritySession, nil, &attrs)
exit((result == 0 && attrs.contains(.sessionHasGraphicAccess)) ? 0 : 1)
EOF
)
}

if [ "$(uname)" = "Darwin" ]; then
  if check_macos_gui; then
    echo "Mac GUI session"
  elif [ -n "$DISPLAY" ]; then
    echo "Mac X11 GUI session"
  else
    echo "Mac non-GUI session"
  fi
elif [ -n "$DISPLAY" ]; then
  echo "X11 GUI session"
fi

Macs can have an X server installed, in which case DISPLAY is defined. However, I don't know if your Electron app will work properly in that configuration. So, I detected it separately.

Answer 2

Here is a working example:

if [ x$DISPLAY != x ] ; then
  echo "GUI Enabled"

else
  echo "GUI Disabled"

fi

All this does is checks the $DISPLAY variable.