max / alloy

Keep dd's progress on a terminal, where its carriage returns mean something `status=progress` redraws a single line. With no cursor to move — a log, a pipe, an agent transcript — every update is kept instead, and a five-gigabyte write arrives as one line thousands of characters long with the only interesting part at the far end. A terminal still gets the live line. Everything else gets dd's default, which prints the transfer summary once at the end, which is all a log wanted from it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: Max Johnson <me@maxj.phd> · 2026-08-09 23:51 UTC

Signed with PGP, not checked

Commit: a9783abcf9dd919da7ca89f28f991124d1ecf7af

Parent: d778a60

1 file changed, +14 insertions, -1 deletion

M build/write-device.sh +14 -1

			@@ -64,7 +64,20 @@
64	64		[ "$reply" = "$DEVICE" ] \|\| die "confirmation did not match; not writing"
65	65
66	66		echo "==> Writing $ARTIFACT to $DEVICE"
67		-	sudo dd if="$ARTIFACT" of="$DEVICE" bs=4M oflag=direct conv=fsync status=progress
	67	+	# `status=progress` redraws one line with carriage returns, which is what a
	68	+	# person watching a five-gigabyte write wants and exactly wrong for anything
	69	+	# that keeps what it is given. A log, a pipe or an agent's transcript has no
	70	+	# cursor to move, so every update is retained and the write arrives as a single
	71	+	# line thousands of characters long with the useful part at the far end.
	72	+	#
	73	+	# So the progress goes to a terminal and nowhere else. Without one, dd's default
	74	+	# still prints the transfer summary once, at the end, which is the whole of what
	75	+	# a log wants from it. Checked on stderr because that is where dd writes both.
	76	+	if [ -t 2 ]; then
	77	+	sudo dd if="$ARTIFACT" of="$DEVICE" bs=4M oflag=direct conv=fsync status=progress
	78	+	else
	79	+	sudo dd if="$ARTIFACT" of="$DEVICE" bs=4M oflag=direct conv=fsync
	80	+	fi
68	81		sync
69	82
70	83		# Verify, because dd reporting success is not evidence the bytes landed.