Driving an interactive program from a script with macterm

[thdxg]

A pipe can't help you with a REPL, a debugger, an ncurses installer, or a paged diff — those programs draw to a terminal and read keys, they don't read stdin and write stdout. macterm pane dump reads the terminal's own cells, so a script outside the pane can see exactly what's on screen and type into it.

Three verbs:

pane run <text>	Type text plus a newline into a live pane's shell or REPL
pane key <chord>	Send one encoded keypress — ctrl+c, ctrl+d, escape, up
pane dump	Print what the pane is displaying (add --scrollback for history)

Worked example: feed a REPL, read the answer

Editor in pane 1, REPL in pane 2:

macterm pane run --pane pane:2 python3
echo 'print("sum:", sum(range(10)))' > /tmp/snippet.py
macterm pane run --pane pane:2 "exec(open('/tmp/snippet.py').read())"
macterm pane dump --pane pane:2 | tail -3

>>> exec(open('/tmp/snippet.py').read())
sum: 45
>>>

pane key ctrl+d exits the REPL; pane key ctrl+c interrupts whatever is running.

Targeting

• --pane pane:2 is the 1-based index within the active tab — stable for a fixed split, and the easiest way to mean "the pane next to me".
• --session macterm-… is restart-stable: pane UUIDs regenerate every launch, session names persist. Get them from macterm pane list.
• Inside a pane, $MACTERM_SESSION is already its own session, so a bare macterm pane split self-targets.

Wait for a sentinel, not a sleep

There's no reliable "is it done" signal to poll — so have the command leave a mark and wait for that:

rm -f /tmp/done
macterm pane run --pane pane:2 "/bin/sh -c 'make test; echo ok > /tmp/done'"
until [ -f /tmp/done ]; do sleep 0.5; done
macterm pane dump --pane pane:2 | tail -20

Wrap anything with a redirect in /bin/sh -c '…'. Text you type lands in the user's shell, and shells disagree: in nushell > is a comparison operator, not a redirect, so a bare echo ok > /tmp/done silently writes no file. Single quotes are fine when typing directly into a pane.

Polling the screen for a marker works too, but the line you typed is echoed on screen, so a naive grep matches your own command. Assemble the marker at runtime — type printf done-%s $NONCE so the joined string only ever exists in the output.

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The same three verbs are what let an AI agent work in a terminal it isn't running inside: pane run to act, pane dump to see the result — including from programs whose output never reaches a pipe.