// A self-feeding tail: the bottom pane appends a timestamp to a log ten
// times a second, the live pane above follows it. Unlike `follow.kdl`
// this needs no second terminal — the dashboard is its own writer, so
// the follower has something to show the moment it starts. Run it:
//
// rat dashboard examples/tail.kdl
//
// and delete /tmp/rat-tail-demo.log when you are done; nothing here
// truncates it. `tail-windows.kdl` is the same dashboard for cmd.
//
// Both panes are `shell #true`, so each command is one script string
// rather than an argv: the follower has no shell syntax in it, but the
// writer's `>>` is a redirect and needs a shell to mean anything.
defaults height=5 border="none" shell=#true interval="never"
// `-F` rather than `-f`, because the log does not exist until the pane
// below writes it and `-F` waits instead of exiting. That is worth more
// than it looks: `interval "never"` on a live pane means no replacement
// child, so a follower that exits at startup stays dead.
pane "a" live=#true {
command #"tail -n 5 -F /tmp/rat-tail-demo.log"#
}
// Whole seconds, because `%N` is a GNU date extension — BSD date, and so
// macOS, prints a literal `N` for it. On GNU coreutils `+%H:%M:%S.%N`
// makes the 100ms cadence much easier to see.
pane "b" {
command #"date +%H:%M:%S >> /tmp/rat-tail-demo.log"#
interval "100ms"
}