sigusr1test.sh

echo "Send signals from another console:"
echo "kill -USR1 $$"

SIG='force'
trap "SIG='USR1'" USR1

# Create a dummy FIFO. Reading the FIFO will block until interrupted by a signal
SIGFIFO="clip.fifo"
if [ ! -p "$SIGFIFO" ]; then
    rm -f "$SIGFIFO"
    mkfifo -m 400 "$SIGFIFO"
fi

while true; do
    echo "SIG='$SIG'"
    if [ -z "$SIG" ]; then
        echo "Waiting..."
        # Redirect stderr to /dev/null to avoid "Interrupted system call"
        # messages. Save stderr to fd 3 so we can restore it later.
        exec 3>&2 2>/dev/null
        # Block until a signal is received
        read < "$SIGFIFO" || true
        exec 2>&3 3>&-
    fi
    # This is _not_ a potential race: the current display is read after this.
    SIG=''

    echo "Doing some work..."
    sleep 3
    echo "Done."
done