macOS screenshots to both clipboard and file via launchd WatchPaths

macOS screenshot settings (com.apple.screencapture) support either target = clipboard (clipboard only, no file) or saving to a location (file only, no clipboard). There is no native "both" option.

Solution

Set macOS to save screenshots to a folder, then use a launchd agent with WatchPaths to auto-copy each new screenshot to the clipboard.

1. Set screenshot target to file

defaults write com.apple.screencapture location ~/Pictures/Screenshots
defaults delete com.apple.screencapture target  # removes clipboard-only mode

Critical: kill screencaptureui after changing defaults — it caches settings and won't re-read them until relaunched:

killall screencaptureui

killall SystemUIServer is NOT sufficient on modern macOS (Sequoia+). The screencaptureui process is separate and long-lived (runs for weeks).

2. Clipboard copy script

Place at ~/.local/bin/screenshot-to-clipboard.sh:

#!/bin/bash
sleep 0.5  # let the file finish writing

NEWEST=$(ls -t "$HOME/Pictures/Screenshots"/*.png 2>/dev/null | head -1)
[ -z "$NEWEST" ] && exit 0

osascript -l JavaScript -e '
function run(argv) {
    ObjC.import("AppKit");
    var data = $.NSData.dataWithContentsOfFile(argv[0]);
    if (data.isNil()) return "file not found";
    var pb = $.NSPasteboard.generalPasteboard;
    pb.clearContents;
    pb.setDataForType(data, $.NSPasteboardTypePNG);
    return "ok";
}' -- "$NEWEST"

Key detail: AppleScript's read ... as class PNGf is broken on modern macOS (error -1700). Use JXA with NSPasteboard.setDataForType instead.

3. launchd agent

Create a plist at ~/Library/LaunchAgents/ with:

• ProgramArguments: /bin/bash and the absolute path to the script above
• WatchPaths: the absolute path to your screenshots folder
• ThrottleInterval: 1

Load with: launchctl bootstrap gui/$(id -u) <plist-path>

Note: launchd plists require absolute paths — expand ~ to your actual home directory.

Gotchas

• Clipboard lands ~3-5 seconds after the screenshot due to WatchPaths trigger delay + osascript JVM startup + 0.5s sleep. Acceptable for most workflows.
• All native shortcuts work unchanged (Cmd+Shift+3, Cmd+Shift+4, Cmd+Shift+5 overlay).
• defaults write is not enough — you must kill screencaptureui (not SystemUIServer) for changes to take effect.