Small changes to 'set -u' handling, a bit of tidying and cleanup

README.md

@@ -22,7 +22,7 @@ Run `zramctl` during use to monitor swap compression and real memory usage.
 
 ### Debugging
 
-Either start zram-swap.sh with `bash -x zram-swap.sh` or `./zram-swap.sh -x (start|stop)` to see what's going wrong.
+Start zram-swap.sh with `bash -x zram-swap.sh (start|stop)` or `./zram-swap.sh -x (start|stop)` to see what's going wrong.
 
 To dump the full execution trace during service start/stop edit  /etc/systemd/systemd/zram-swap.service and add -x to the following two lines:
 

install.sh

@@ -8,8 +8,13 @@ if systemctl -q is-active zram-swap.service; then
 fi
 
 install -o root zram-swap.sh /usr/local/sbin/zram-swap.sh
-install -o root zram-swap-service /etc/default/zram-swap-service
-install -o root zram-swap.service /etc/systemd/system/zram-swap.service
+if [[ -f /etc/default/zram-swap-service ]]; then
+  mv -f /etc/default/zram-swap-service /etc/default/zram-swap
+  chmod 0644 /etc/default/zram-swap
+else
+  install -o root -m 0644 service/zram-swap.config /etc/default/zram-swap
+fi
+install -o root -m 0644 service/zram-swap.service /etc/systemd/system/zram-swap.service
 
 systemctl daemon-reload
 systemctl enable zram-swap.service

service/zram-swap.config

@@ -0,0 +1,18 @@
+# portion of real ram to use as zram swap (expression: "1/2", "0.5", etc)
+_zram_fraction="1/2"
+
+# compression algorithm to employ (lzo, lz4, zstd, lzo-rle)
+_zram_algorithm="lz4"
+
+# expected compression ratio; this is a rough estimate
+#_comp_factor="2.5"
+
+# Note:
+# set _comp_factor by hand if you use an algorithm other than lzo/lz4/zstd or if your
+# use case produces drastically different compression results than my estimates
+#
+# defaults if otherwise unset:
+#	lzo*|zstd)  _comp_factor="3"   ;;
+#	lz4)        _comp_factor="2.5" ;;
+#	*)          _comp_factor="2"   ;;
+#

zram-swap-service

@@ -1,22 +0,0 @@
-# portion of real ram to use as zram swap (expression: "1/2", "0.5", etc)
-_zram_fraction="1/2"
-
-# compression algorithm to employ (lzo, lz4, zstd, lzo-rle)
-_zram_algorithm="lz4"
-
-# set expected compression ratio based on algorithm; this is a rough estimate
-# set this by hand if you use an algorithm other than lzo/lz4/zstd
-#_comp_factor="2.5"
-#
-# defaults:
-#case $_zram_algorithm in
-#	lzo*|zstd)
-#		_comp_factor="3"
-#		;;
-#	lz4)
-#		_comp_factor="2.5"
-#		;;
-#	*)
-#		_comp_factor="2"
-#		;;
-#esac

zram-swap.sh

@@ -2,10 +2,15 @@
 # source: https://github.com/foundObjects/zram-swap
 
 [[ "$EUID" == "0" ]] || { echo "This script requires root." && exit 1; }
-set -eo pipefail
+set -euo pipefail
 
-# parse debug flag early so we can trace everything
-[[ "$1" == "-x" ]] && { shift && set -x; } >&/dev/null
+# make sure our environment is predictable
+PATH=/usr/sbin:/usr/bin:/sbin:/bin
+unalias -a
+# parse debug flag early so we can trace user configuration
+(("$#" > 0)) && [[ "$1" == "-x" ]] && { shift && set -x; } >&/dev/null
+# make sure $1 exists for 'set -u' so we can get through 'case "$1"' below
+(("$#" == 0)) && { set -- ""; } >&/dev/null
 
 # set sane defaults, see /etc/default/zram-swap-service for explanations
 _zram_fraction="1/2"
@@ -13,8 +18,8 @@ _zram_algorithm="lz4"
 _comp_factor=''
 
 # load user config
-[[ -f /etc/default/zram-swap-service ]] &&
-  source /etc/default/zram-swap-service
+[[ -f /etc/default/zram-swap ]] &&
+  source /etc/default/zram-swap
 
 # set expected compression ratio based on algorithm; this is a rough estimate
 # skip if already set in user config
@@ -34,9 +39,6 @@ _main() {
   fi
 
   case "$1" in
-    # a little magic to quietly set -u after testing our last expected empty variable
-    # matches every case, runs set -u without logging to the trace and then continues matching
-    *) { set -u; } 2>/dev/null ;;&
     "init" | "start")
       if grep -q zram /proc/swaps; then
         err "zram swap already in use, exiting"
@@ -52,8 +54,8 @@ _main() {
       _end
       ;;
     *)
-      echo "Usage: $0 (init|end)"
-      return 1
+      _usage
+      exit 1
       ;;
   esac
 }
@@ -89,7 +91,7 @@ _init() {
 # end swapping and cleanup
 _end() {
   local ret="0"
-  DEVICES=$(grep zram /proc/swaps | awk '{print $1}')
+  DEVICES=$(awk '/zram/ {print $1}' /proc/swaps)
   for d in $DEVICES; do
     swapoff "$d"
     if ! _rem_zdev "$d"; then
@@ -121,5 +123,6 @@ _rem_zdev() {
 calc() { awk "BEGIN{print $*}"; }
 #crapout() { echo "$@" >&2 && exit 1; }
 err() { echo "Err '${FUNCNAME[1]}': $*" >&2; }
+_usage() { echo "Usage: $(basename "$0") (init|end)"; }
 
 _main "$@"