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diff --git a/pipeline/alarm-lib.sh b/pipeline/alarm-lib.sh
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+#!/bin/bash
+#
+# Alarm tool.
+#
+# Usage:
+#   ./alarm.sh <function name>
+
+# You can source this file and use the alarm-status function.
+
+set -o nounset
+set -o pipefail
+set -o errexit
+
+# Run a command with a timeout, and print its status to a directory.
+#
+# Usage:
+#   alarm-status job_dir/STATUS 10 \
+#     flaky_command ...
+
+alarm-status() {
+  set +o errexit
+  local status_file=$1
+  shift  # everything except the status file goes to perl
+
+  # NOTE: It would be nice to setpgrp() before exec?  And then can the signal
+  # be delivered to the entire group, like kill -SIGALRM -PID?
+
+  # NOTE: If we did this in Python, the error message would also be clearer.
+  perl -e 'alarm shift; exec @ARGV or die "ERROR: after exec @ARGV"' "$@" 
+  local exit_code=$?
+
+  set -o errexit
+
+  local result=''
+  case $exit_code in
+    0)
+      # Would be nice to show elapsed time?
+      result='OK'
+      ;;
+    9)
+      # decode_assoc.R will exit 9 if there are no reports AFTER
+      # --remove-bad-rows.  A task can also be marked SKIPPED before running
+      # the child process (see backfill.sh).
+      result='SKIPPED by child process'
+      ;;
+    # exit code 142 means SIGALARM.  128 + 14 = 142.  See 'kill -l'.
+    142)
+      local seconds=$1
+      result="TIMEOUT after $seconds seconds"
+      ;;
+    *)
+      result="FAIL with status $exit_code"
+      ;;
+  esac
+  echo "$result"
+  echo "$result" > $status_file
+}
+
+_work() {
+  local n=10  # 2 seconds
+  for i in $(seq $n); do
+    echo $i - "$@"
+    sleep 0.2
+  done
+}
+
+_succeed() {
+  _work "$@"
+  exit 0
+}
+
+_fail() {
+  _work "$@"
+  exit 1
+}
+
+_skip() {
+  exit 9
+}
+
+# http://perldoc.perl.org/functions/alarm.html
+#
+# Delivers alarm.  But how to get the process to have a distinct exit code?
+
+demo() {
+  mkdir -p _tmp
+
+  # timeout
+  alarm-status _tmp/A 1 $0 _succeed foo
+  echo
+
+  # ok
+  alarm-status _tmp/B 3 $0 _succeed bar
+  echo
+
+  # fail
+  alarm-status _tmp/C 3 $0 _fail baz
+  echo
+
+  # skip
+  alarm-status _tmp/D 3 $0 _skip baz
+  echo
+
+  head _tmp/{A,B,C,D}
+}
+
+test-simple() {
+  alarm-status _tmp/status.txt 1 sleep 2
+}
+
+test-bad-command() {
+  alarm-status _tmp/status.txt 1 nonexistent_sleep 2
+}
+
+# BUG
+test-perl() {
+  set +o errexit
+  perl -e 'alarm shift; exec @ARGV or die "ERROR after exec @ARGV"' 1 _sleep 2
+  echo $?
+}
+
+if test $(basename $0) = 'alarm-lib.sh'; then
+  "$@"
+fi