respawn: add seperate shell utility instead of running while loops

Technically, these are the same shell commands, but since they are run
by a separate shell, they are easier to predict and easier to kill.

3 files changed, 26 insertions, 3 deletions

diff --git a/contrib/getty.boot b/contrib/getty.boot
index bb5a5e3..eaf90d9 100644
--- a/contrib/getty.boot
+++ b/contrib/getty.boot
@@ -1,4 +1,4 @@
 for getty in 1 2 3 4 5 6; do
-    while :; do /sbin/getty 38400 tty${getty} 2>&1 ; done &  # busybox getty
-    while :; do /sbin/getty /dev/tty${getty} linux 2>&1 ; done &  # ubase getty
+    respawn getty 38400 tty${getty} 2>&1 ; done &  # busybox getty
+    respawn getty /dev/tty${getty} linux 2>&1 ; done &  # ubase getty
 done
diff --git a/contrib/respawn b/contrib/respawn
new file mode 100644
index 0000000..1b914ea
--- /dev/null
+++ b/contrib/respawn
@@ -0,0 +1,23 @@
+#!/bin/sh -e
+# POSIX shell variant for ubase respawn
+
+usage() {
+    printf 'usage: %s [-d N] cmd [args...]\n' "${0##*/}"
+    exit "${1:-0}"
+}
+
+die() { printf '%s\n' "$@" >&2; exit 1;}
+
+case "$1" in
+    -d) [ "$3" ] || usage 1
+        [ "$2" -gt 0 ] || die "Not a number: $2"
+        delay=$2; shift 2
+        ;;
+    --help|-h|'') usage ;;
+    -*) usage 1
+esac
+
+while :; do
+    "$@"
+    [ "$delay" ] && sleep "$delay"
+done
diff --git a/contrib/runit.boot b/contrib/runit.boot
index aafe142..f8858c9 100644
--- a/contrib/runit.boot
+++ b/contrib/runit.boot
@@ -1 +1 @@
-while :; do /usr/bin/runsvdir -P /var/service ; done &
+respawn runsvdir -P /var/service ; done &