sfeed_update: handle signals consistently in different shells

- Handle SIGTERM properly, don't leave stray processes. Kill them on both
  SIGTERM and SIGINT.
- When a "batch" of feeds was interrupted, don't allow to wait again.
- Simplify and create sighandler function.
- Now on both SIGTERM and SIGINT the cleanup() handler is called to not leave
  stray files.

Tested with ksh, dash, bash, zsh.

1 files changed, 16 insertions, 11 deletions

diff --git a/sfeed_update b/sfeed_update
index e2f9677..5ee99ee 100755
--- a/sfeed_update
+++ b/sfeed_update
@@ -77,8 +77,9 @@ fetchfeed() {
 feed() {
 	# wait until ${maxjobs} are finished: throughput using this logic is
 	# non-optimal, but it is simple and portable.
+	[ ${signo} -ne 0 ] && return
 	[ $((curjobs % maxjobs)) -eq 0 ] && wait
-	[ ${isinterrupted} -eq 1 ] && return
+	[ ${signo} -ne 0 ] && return
 	curjobs=$((curjobs + 1))
 
 	(name="$1"
@@ -123,8 +124,12 @@ cleanup() {
 	rm -rf "${sfeedtmpdir}"
 }
 
-interrupted() {
-	isinterrupted=1
+sighandler() {
+	signo="$1"
+	# ignore TERM signal for myself.
+	trap -- "" TERM
+	# kill all running childs >:D
+	kill -TERM -$$
 }
 
 feeds() {
@@ -134,12 +139,12 @@ feeds() {
 
 # job counter.
 curjobs=0
-# kill whole current process group on ^C (SIGINT).
-isinterrupted=0
+# signal number received for parent.
+signo=0
+# SIGINT: signal to interrupt parent.
+trap -- "sighandler 2" "INT"
 # SIGTERM: signal to terminate parent.
-trap -- "interrupted" "TERM"
-# SIGINT: kill all running childs >:D
-trap -- "kill -TERM -$$" "INT"
+trap -- "sighandler 15" "TERM"
 # load config file.
 loadconfig "$1"
 # fetch feeds and store in temporary file.
@@ -149,9 +154,9 @@ mkdir -p "${sfeedpath}"
 # fetch feeds specified in config file.
 feeds
 # wait till all feeds are fetched (concurrently).
-wait
+[ ${signo} -eq 0 ] && wait
 # cleanup temporary files etc.
 cleanup
-# on SIGINT exit with 128 + signal (SIGINT = 2).
-[ ${isinterrupted} -eq 1 ] && exit 130
+# on signal SIGINT and SIGTERM exit with signal number + 128.
+[ ${signo} -ne 0 ] && exit $((signo+128))
 exit 0