Initial import of nq

1 files changed, 67 insertions, 0 deletions

diff --git a/nq.sh b/nq.sh
new file mode 100755
index 0000000..2907be5
--- /dev/null
+++ b/nq.sh
@@ -0,0 +1,67 @@
+#!/bin/sh
+# nq CMD... - run CMD... in background and in order, saving output to ,* files
+#
+# - needs POSIX sh + util-linux flock(1)
+# - when run from tmux, display output in a new window (needs
+#   GNU tail, C-c to abort the job.)
+# - we try hard to make the currently running ,* file have +x bit
+# - enforcing order works like this:
+#   - every job has a flock(2)ed file
+#   - every job starts only after all earlier flock(2)ed files finished
+#   - the lock is released when job terminates
+#
+# To the extent possible under law, Christian Neukirchen <chneukirchen@gmail.com>
+# has waived all copyright and related or neighboring rights to this work.
+# http://creativecommons.org/publicdomain/zero/1.0/
+
+if [ -z "$NQ" ]; then
+	export NQ=$(date +%s)
+	"$0" "$@" & c=$!
+	(
+		# wait for job to finish
+		flock -x .,$NQ.$c -c true
+		flock -x ,$NQ.$c -c true
+		chmod -x ,$NQ.$c
+	) &
+	exit
+fi
+
+us=",$NQ.$$"
+
+exec 9>>.$us
+# first flock(2) the file, then make it known under the real name
+flock -x 9
+mv .$us $us
+
+printf "## nq $*" 1>&9
+
+if [ -n "$TMUX" ]; then
+	tmux new-window -a -d -n '<' -c '#{pane_current_path}' \
+		"trap true INT QUIT TERM EXIT;
+                 tail -F --pid=$$ $us || kill $$;
+		 printf '\n[%d exited, ^D to exit.]\n' $$;
+		 cat >/dev/null"
+fi
+    
+waiting=true
+while $waiting; do
+	waiting=false
+	# this must traverse in lexical (= numerical) order:
+        # check all older locks are released
+	for f in ,*; do
+		# reached the current lock, good to go
+		[ $f = $us ] && break
+
+		if ! flock -x -n $f -c "chmod -x $f"; then
+			# force retrying all locks again;
+			# an earlier lock could just now have really appeared
+			waiting=true
+			flock -x $f -c true
+		fi
+	done
+done
+
+printf '\n' 1>&9
+
+chmod +x $us
+exec "$@" 2>&1 1>&9