1 files changed, 49 insertions, 0 deletions
diff --git a/pkgs/simple/xdpytools/src/xdpysel b/pkgs/simple/xdpytools/src/xdpysel
new file mode 100755
index 0000000..e080155
--- /dev/null
+++ b/pkgs/simple/xdpytools/src/xdpysel
@@ -0,0 +1,49 @@
+#! /bin/sh
+# usage: xdpysel {prev,next}
+# Print the number of the selected X display.
+
+find /tmp/.X11-unix -mindepth 1 -maxdepth 1 |
+jq -Rrs --arg command "$1" '
+  (
+    split("\n") |
+    map(
+      select(.!="") |
+      match("^.*/X([0-9]+)$").captures[0].string |
+      tonumber
+    )
+  )
+    as $all_displays |
+
+  (
+    env.DISPLAY |
+    match("^:([0-9]+)(?:[.][0-9]+)?$").captures[0].string |
+    tonumber
+  )
+    as $current_display |
+
+  ($all_displays | length) as $all_displays_count |
+
+  ($all_displays|index($current_display))
+    as $current_index |
+
+  (($current_index + 1) % $all_displays_count)
+    as $next_index |
+
+  (($all_displays_count + $current_index - 1) % $all_displays_count)
+    as $prev_index |
+
+  $all_displays[$prev_index] as $prev_display |
+  $all_displays[$next_index] as $next_display |
+
+  {
+    prev: $prev_display,
+    next: $next_display,
+  }[$command]
+    as $result |
+
+  if $result | type == "number" then
+    $result
+  else
+    "xdpysel: bad argument: \($command)\n" | halt_error(-1)
+  end
+'