diff --git a/plugins/debian/deborphan b/plugins/debian/deborphan
index 10d5ac44..633ac7df 100755
--- a/plugins/debian/deborphan
+++ b/plugins/debian/deborphan
@@ -76,7 +76,7 @@ EOF
 else
   for CAT in ${CATEGORIES}; do
     CATFIELD=$(clean_fieldname "${CAT}")
-    CATDATA=$(echo "${OUT}" | sed -n "s#${CAT} \+##p")
+    CATDATA=$(echo "${OUT}" | sed -n 's#'"${CAT}"' \+##p')
     echo "${CATFIELD}.value $(echo "${CATDATA}" | wc -l)"
     echo "${CATFIELD}.extinfo $(echo "${CATDATA}" | tr '\n' ' ')"
   done
diff --git a/plugins/debian/debsecan_ b/plugins/debian/debsecan_
index c78a797d..7ef84e1d 100755
--- a/plugins/debian/debsecan_
+++ b/plugins/debian/debsecan_
@@ -169,7 +169,7 @@ case "${MODE}" in
 esac
 
 # Reformat the output of the cut|sort|uniq... to a more human-friendly "item (count)" format
-CVECOUNTRE="s/^ *\([0-9]\+\) \+\([^ ]\+\)/\2 (\1)/"
+CVECOUNTRE='s/^ *\([0-9]\+\) \+\([^ ]\+\)/\2 (\1)/'
 
 # shellcheck disable=SC2005 disable=SC2046
 # The nested $(echo ...)s are needed to yet the newlines
diff --git a/plugins/ejabberd/ejabberd_stats_ b/plugins/ejabberd/ejabberd_stats_
index 9eb7c184..42200fad 100755
--- a/plugins/ejabberd/ejabberd_stats_
+++ b/plugins/ejabberd/ejabberd_stats_
@@ -22,7 +22,7 @@
 #%# capabilities=autoconf suggest
 
 EJABBERDCTL=${ejabberdctl:-$(which ejabberdctl)}
-SCRIPT_NAME=$(basename $0)
+SCRIPT_NAME=$(basename "$0")
 STATS_TYPE="${SCRIPT_NAME/ejabberd_stats_/}"
 
 function ejabberd_stats_connected_users() {
@@ -81,4 +81,4 @@ SUGGESTIONS
 		;;
 esac
 
-ejabberd_stats_${STATS_TYPE} $1
+"ejabberd_stats_${STATS_TYPE}" "$1"
diff --git a/plugins/ilias/ilias_session b/plugins/ilias/ilias_session
index 5f85a7c4..ad227ebf 100755
--- a/plugins/ilias/ilias_session
+++ b/plugins/ilias/ilias_session
@@ -154,6 +154,7 @@ config() {
     # -v varname
     # True if the shell variable varname is set (has been assigned a value).
     # https://stackoverflow.com/a/45385463/2683737
+    # shellcheck disable=SC2102
     while [[ -v d_attr[$i,field] ]]; do
        field=${d_attr[$i,field]}
        echo "$field.type ${d_attr[$i,type]}"
@@ -181,6 +182,7 @@ fetch() {
 
     # create an array of queries
     i=0
+    # shellcheck disable=SC2102
     while [[ -v d_attr[$i,field] ]]; do
         query+=("${d_attr[$i,sql]}")
         ((++i))
@@ -211,6 +213,7 @@ fetch() {
     # extract result and echo it to stdout, which is
     # captured by Munin
     i=0
+    # shellcheck disable=SC2102
     while [[ -v d_attr[$i,field] ]]; do
         echo "${d_attr[$i,field]}.value ${results[$i]}"
         ((++i))
diff --git a/plugins/minecraft/minecraft-users-ram_ b/plugins/minecraft/minecraft-users-ram_
index 0520935d..1de3aaa7 100755
--- a/plugins/minecraft/minecraft-users-ram_
+++ b/plugins/minecraft/minecraft-users-ram_
@@ -49,7 +49,7 @@ fi
 
 PLAYERCOUNT=$(LC_LANG=C netstat -tn | grep ":$MC_PORT " | grep ESTABLISHED | wc -l)
 MC_PID=$(netstat -tlpn | grep ":$MC_PORT " | sed -n -e '1p' | awk '{ print $7 }' | cut -d '/' -f1)
-if [ ! -z "${MC_PID}" ]
+if [ -n "${MC_PID}" ]
 then #is running
     MEMGiB=$(ps -p "$MC_PID" -o rss | sed -n '2p' | awk '{ print $1 / 1024 / 1024 }')
     CPU=$(top -bp "$MC_PID" -n 1 | sed -n '$p' | awk '{ print $10 / 100; }')
diff --git a/plugins/munin/munin_events b/plugins/munin/munin_events
index 2a355bd9..73f36dd0 100755
--- a/plugins/munin/munin_events
+++ b/plugins/munin/munin_events
@@ -71,7 +71,7 @@ do_value() {
     FIELD="$1"
     EVENT_LABEL="$2"
 
-    EVENT_COUNT="$("$logtail_bin" -t "$muninupdate" 2> /dev/null | grep -c "^[0-9/: ]\{19\} \[${EVENT_LABEL}\]")"
+    EVENT_COUNT="$("$logtail_bin" -t "$muninupdate" 2> /dev/null | grep -c '^[0-9/: ]\{19\} \['"${EVENT_LABEL}"'\]')"
     if echo "$EVENT_COUNT" | grep -q "[^0-9]"; then
         echo "Cannot determine event count" 1>&2
         exit 10
diff --git a/plugins/nfs-freebsd/nfs_client b/plugins/nfs-freebsd/nfs_client
index 312fb6f2..ef930f4e 100755
--- a/plugins/nfs-freebsd/nfs_client
+++ b/plugins/nfs-freebsd/nfs_client
@@ -37,16 +37,16 @@ if [ "$1" = "autoconf" ]; then
     fi
 fi
 
-labels=`$NFSSTAT -c | grep -iv "[0-9]" | grep -v ":" | sed 's/X\ /x_/' | tr '\n' ' ' | awk '{print $1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13,$14,$15,$16,$17,$18,$19,$20,$21,$22,$23,$24,$25,$26}' | tr '[A-Z]' '[a-z]'`
-values=`$NFSSTAT -c | grep -i "[0-9]" | tr '\n' ' ' | awk '{print $1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13,$14,$15,$16,$17,$18,$19,$20,$21,$22,$23,$24,$25,$26}'`
+labels=$("$NFSSTAT" -c | grep -iv "[0-9]" | grep -v ":" | sed 's/X\ /x_/' | tr '\n' ' ' | awk '{print $1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13,$14,$15,$16,$17,$18,$19,$20,$21,$22,$23,$24,$25,$26}' | tr '[:upper:]' '[:lower:]')
+values=$("$NFSSTAT" -c | grep -i "[0-9]" | tr '\n' ' ' | awk '{print $1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13,$14,$15,$16,$17,$18,$19,$20,$21,$22,$23,$24,$25,$26}')
 
-larray=( $labels )
-varray=( $values )
+read -r -a larray <<<"$labels"
+read -r -a varray <<<"$values"
 if [ "$1" = "config" ]; then
 
     echo 'graph_title NFSv3 Client'
     echo 'graph_args --base 1000 -l 0'
-    echo 'graph_vlabel requests / ${graph_period}'
+    echo "graph_vlabel requests / \${graph_period}"
     echo 'graph_total total'
     echo 'graph_category fs'
     for a in $labels; do echo "$a.label $a" ; echo "$a.type DERIVE"; echo "$a.min 0"; done
diff --git a/plugins/nfs-freebsd/nfs_client_cache b/plugins/nfs-freebsd/nfs_client_cache
index 9c5d3441..3be86392 100755
--- a/plugins/nfs-freebsd/nfs_client_cache
+++ b/plugins/nfs-freebsd/nfs_client_cache
@@ -37,16 +37,16 @@ if [ "$1" = "autoconf" ]; then
     fi
 fi
 
-labels=`$NFSSTAT -c | grep -iv "[0-9]" | tail -n 2 | sed 's/BioRLHits/BioRL\ Hits/g' | awk '{print $1"_"$2,$1"_"$3,$4"_"$5,$4"_"$6,$7"_"$8,$7"_"$9,$10"_"$11,$10"_"$12}' | tr '\n' ' ' | tr '[A-Z]' '[a-z]'`
-values=`$NFSSTAT -c | grep -i "[0-9]" | tail -n 2 | tr '\n' ' '`
+labels=$("$NFSSTAT" -c | grep -iv "[0-9]" | tail -n 2 | sed 's/BioRLHits/BioRL\ Hits/g' | awk '{print $1"_"$2,$1"_"$3,$4"_"$5,$4"_"$6,$7"_"$8,$7"_"$9,$10"_"$11,$10"_"$12}' | tr '\n' ' ' | tr '[:upper:]' '[:lower:]')
+values=$("$NFSSTAT" -c | grep -i "[0-9]" | tail -n 2 | tr '\n' ' ')
 
-larray=( $labels )
-varray=( $values )
+read -r -a larray <<<"$labels"
+read -r -a varray <<<"$values"
 if [ "$1" = "config" ]; then
 
     echo 'graph_title NFSv3 Client Cache'
     echo 'graph_args --base 1000 -l 0'
-    echo 'graph_vlabel requests / ${graph_period}'
+    echo "graph_vlabel requests / \${graph_period}"
     echo 'graph_total total'
     echo 'graph_category fs'
     for a in $labels; do echo "$a.label $a" ; echo "$a.type DERIVE"; echo "$a.min 0"; done
diff --git a/plugins/nfs-freebsd/nfsd b/plugins/nfs-freebsd/nfsd
index d551b844..d2e3d848 100755
--- a/plugins/nfs-freebsd/nfsd
+++ b/plugins/nfs-freebsd/nfsd
@@ -38,17 +38,17 @@ if [ "$1" = "autoconf" ]; then
     fi
 fi
 
-labels=`$NFSSTAT -s | grep -iv "[0-9]" | grep -v ":" | sed 's/Server\ //' | tr '\n' ' ' | awk '{print $1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13,$14,$15,$16,$17,$18,$19,$20,$21,$22,$23,$24,$25,$26,$27,$28,$29,$30}' | tr '[A-Z]' '[a-z]'`
-values=`$NFSSTAT -s | grep -i "[0-9]" | tr '\n' ' ' | awk '{print $1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13,$14,$15,$16,$17,$18,$19,$20,$21,$22,$23,$24,$25,$26,$27,$28,$29,$30}'`
+labels=$("$NFSSTAT" -s | grep -iv "[0-9]" | grep -v ":" | sed 's/Server\ //' | tr '\n' ' ' | awk '{print $1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13,$14,$15,$16,$17,$18,$19,$20,$21,$22,$23,$24,$25,$26,$27,$28,$29,$30}' | tr '[:upper:]' '[:lower:]')
+values=$("$NFSSTAT" -s | grep -i "[0-9]" | tr '\n' ' ' | awk '{print $1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13,$14,$15,$16,$17,$18,$19,$20,$21,$22,$23,$24,$25,$26,$27,$28,$29,$30}')
 
-larray=( $labels )
-varray=( $values )
+read -r -a larray <<<"$labels"
+read -r -a varray <<<"$values"
 
 if [ "$1" = "config" ]; then
 
     echo 'graph_title NFSv3 Server'
     echo 'graph_args --base 1000 -l 0'
-    echo 'graph_vlabel requests / ${graph_period}'
+    echo "graph_vlabel requests / \${graph_period}"
     echo 'graph_total total'
     echo 'graph_category fs'
     for a in $labels; do echo "$a.label $a" ; echo "$a.type DERIVE"; echo "$a.min 0"; done
diff --git a/plugins/nscd/nscd_ b/plugins/nscd/nscd_
index b8919a55..00bde9f8 100755
--- a/plugins/nscd/nscd_
+++ b/plugins/nscd/nscd_
@@ -33,19 +33,23 @@
 #%# family=auto
 #%# capabilities=autoconf suggest
 
-source $MUNIN_LIBDIR/plugins/plugin.sh
+. "$MUNIN_LIBDIR/plugins/plugin.sh"
 NSCD_CFG=${nscd_cfg:-/etc/nscd.conf}
 AUTOCONF_CHECK=$(nscd -g | grep -ic 'yes.*cache is enabled')
-SUGGEST_CHECK=$(nscd -g | grep -iB2 'yes.*cache is enabled' | awk {'print $1'} | head -1)
-MODE=$(basename $0 | sed 's/^nscd_//g' | tr '_' '.')
+SUGGEST_CHECK=$(nscd -g | grep -iB2 'yes.*cache is enabled' | awk '{print $1}' | head -1)
+MODE=$(basename "$0" | sed 's/^nscd_//g' | tr '_' '.')
 
 case $1 in
 	autoconf)
-		[ -r "$NSCD_CFG" ] && [ $AUTOCONF_CHECK -gt 0 ] && echo yes || echo "no (nscd config not found or no database enabled)"
+		if [ -r "$NSCD_CFG" ] && [ "$AUTOCONF_CHECK" -gt 0 ]; then
+			echo yes
+		else
+			echo "no (nscd config not found or no database enabled)"
+		fi
 		exit 0
 		;;
 	suggest)
-		echo $SUGGEST_CHECK
+		echo "$SUGGEST_CHECK"
 		exit 0
 		;;
 	config)
@@ -66,7 +70,7 @@ CONFIG
 		;;
 	fetch|*)
 			nscd -g | awk "/^$MODE cache/ {printline = 1; print; next} /^.*cache:/ {printline = 0} printline" | \
-			egrep '(suggested size|cache hit rate|current number of cached values|maximum number of cached values)' | \
-			sed 's/%//' | awk {' if (NR==1) print "suggestedsize.value " $1; if (NR==2) print "cachehitrate.value " $1; if (NR==3) print "currnumber.value " $1; if (NR==4) print "maxnumber.value " $1'}
+			grep -E '(suggested size|cache hit rate|current number of cached values|maximum number of cached values)' | \
+			sed 's/%//' | awk '{ if (NR==1) print "suggestedsize.value " $1; if (NR==2) print "cachehitrate.value " $1; if (NR==3) print "currnumber.value " $1; if (NR==4) print "maxnumber.value " $1}'
 		;;
 esac
diff --git a/plugins/quake/qstatcod4and5_ b/plugins/quake/qstatcod4and5_
index cf027e34..f1fd36d1 100755
--- a/plugins/quake/qstatcod4and5_
+++ b/plugins/quake/qstatcod4and5_
@@ -64,7 +64,7 @@ quake_stat() {
         port=$3
     fi
 
-    if [ ! -z "$gametype" ] && [ ! -z "$gametype" ] && [ ! -z "$gametype" ]; then
+    if [ -n "$gametype" ] && [ -n "$gametype" ] && [ -n "$gametype" ]; then
         dummy=$("$qstat_exe" -P -pa -sort P "-$gametype" "${ip}:${port}" | grep frags | wc -l)
         playervalue=$dummy
 
diff --git a/plugins/rabbitmq/rabbitmq_connections b/plugins/rabbitmq/rabbitmq_connections
index fd755968..73f770ec 100755
--- a/plugins/rabbitmq/rabbitmq_connections
+++ b/plugins/rabbitmq/rabbitmq_connections
@@ -96,4 +96,4 @@ else
     connections=U
 fi
 
-printf "connections.value %s\n" "$connections"
+printf 'connections.value %s\n' "$connections"
diff --git a/plugins/raspberry-pi/raspi_temp b/plugins/raspberry-pi/raspi_temp
index 55f85e45..5918b4e8 100755
--- a/plugins/raspberry-pi/raspi_temp
+++ b/plugins/raspberry-pi/raspi_temp
@@ -48,4 +48,4 @@ EOM
         exit 0;;
 esac
 
-echo "temp.value $(vcgencmd measure_temp | sed -n "s/temp=\(.*\)\'C/\1/p")"
+echo "temp.value $(vcgencmd measure_temp | sed -n 's/temp=\(.*\)'"'"'C/\1/p')"
diff --git a/plugins/ssl/ssl-certificate-expiry b/plugins/ssl/ssl-certificate-expiry
index f338a8f5..d2d56f30 100755
--- a/plugins/ssl/ssl-certificate-expiry
+++ b/plugins/ssl/ssl-certificate-expiry
@@ -70,7 +70,7 @@ HOSTPORT=${0##*ssl-certificate-expiry_}
 CACHEFILE="${MUNIN_PLUGSTATE}/$(basename "${0}").cache"
 
 if [ "${HOSTPORT}" != "${0}" ] \
-	&& [ ! -z "${HOSTPORT}" ]; then
+	&& [ -n "${HOSTPORT}" ]; then
 	services="${HOSTPORT}"
 fi
 
diff --git a/plugins/ssl/ssl_ b/plugins/ssl/ssl_
index 496453f1..5c1c4fcc 100755
--- a/plugins/ssl/ssl_
+++ b/plugins/ssl/ssl_
@@ -84,4 +84,4 @@ cert=$(echo "" | openssl s_client -CApath /etc/ssl/certs -servername "${SITE}" -
 days_left=$(echo "$cert" | parse_valid_days_from_certificate)
 [ -n "$days_left" ] || days_left="U"
 
-printf "expire.value %s\n" "$days_left"
+printf 'expire.value %s\n' "$days_left"
diff --git a/plugins/syncthing/strelaysrv_ b/plugins/syncthing/strelaysrv_
index dabc504e..a5a31927 100755
--- a/plugins/syncthing/strelaysrv_
+++ b/plugins/syncthing/strelaysrv_
@@ -57,10 +57,10 @@ EOM
             NC=$(echo "$STATUS" | $JQ '.numConnections ')
             NK=$(echo "$STATUS" | $JQ '.numPendingSessionKeys ')
             NP=$(echo "$STATUS" | $JQ '.numProxies ')
-            printf "strelaysrv_num_sessions.value %s\n" "$NS"
-            printf "strelaysrv_num_connections.value %s\n" "$NC"
-            printf "strelaysrv_num_pending.value %s\n" "$NK"
-            printf "strelaysrv_num_proxies.value %s\n" "$NP"
+            printf 'strelaysrv_num_sessions.value %s\n' "$NS"
+            printf 'strelaysrv_num_connections.value %s\n' "$NC"
+            printf 'strelaysrv_num_pending.value %s\n' "$NK"
+            printf 'strelaysrv_num_proxies.value %s\n' "$NP"
     esac
 }
 
@@ -77,7 +77,7 @@ EOM
         *)
             STATUS=$(getstatus)
             UPTIME=$(echo "$STATUS" | "$JQ" '.uptimeSeconds')
-            printf "strelaysrv_uptime.value %s\n" "$UPTIME"
+            printf 'strelaysrv_uptime.value %s\n' "$UPTIME"
     esac
 }
 
@@ -94,7 +94,7 @@ EOM
         *)
             STATUS=$(getstatus)
             GOROUTINE=$(echo "$STATUS" | "$JQ" '.goNumRoutine')
-            printf "strelaysrv_goroutine.value %s\n" "$GOROUTINE"
+            printf 'strelaysrv_goroutine.value %s\n' "$GOROUTINE"
     esac
 }
 
@@ -113,7 +113,7 @@ EOM
 	    *)
             STATUS=$(getstatus)
             BP=$(echo "$STATUS" | "$JQ" '.bytesProxied ')
-            printf "strelaysrv_proxied.value %s\n" "$BP"
+            printf 'strelaysrv_proxied.value %s\n' "$BP"
     esac
 }
 
@@ -132,7 +132,7 @@ EOM
 	    *)
             STATUS=$(getstatus)
             TRANSFER=$(echo "$STATUS" | "$JQ" '.kbps10s1m5m15m30m60m[2] ')
-            printf "strelaysrv_transfer.value %s\n" "$TRANSFER"
+            printf 'strelaysrv_transfer.value %s\n' "$TRANSFER"
     esac
 }
 
diff --git a/plugins/syncthing/syncthing_ b/plugins/syncthing/syncthing_
index 8c7fc8a9..05efc7dd 100755
--- a/plugins/syncthing/syncthing_
+++ b/plugins/syncthing/syncthing_
@@ -57,7 +57,7 @@ EOM
         *)
             STATUS=$(getstatus)
 			CPU=$(echo "$STATUS" | "$JQ" '.cpuPercent')
-            printf "syncthing_cpu.value %s\n" "$CPU"
+            printf 'syncthing_cpu.value %s\n' "$CPU"
     esac
 }
 
@@ -80,8 +80,8 @@ EOM
             STATUS=$(getstatus)
             ALL=$(echo "$STATUS" | "$JQ" '.alloc')
             SYS=$(echo "$STATUS" | "$JQ" '.sys')
-            printf "syncthing_mem_all.value %s\n" "$ALL"
-            printf "syncthing_mem_sys.value %s\n" "$SYS"
+            printf 'syncthing_mem_all.value %s\n' "$ALL"
+            printf 'syncthing_mem_sys.value %s\n' "$SYS"
     esac
 }
 
@@ -98,7 +98,7 @@ EOM
         *)
             STATUS=$(getstatus)
             UPTIME=$(echo "$STATUS" | "$JQ" '.uptime')
-            printf "syncthing_uptime.value %s\n" "$UPTIME"
+            printf 'syncthing_uptime.value %s\n' "$UPTIME"
     esac
 }
 
@@ -115,7 +115,7 @@ EOM
         *)
             STATUS=$(getstatus)
             GOROUTINES=$(echo "$STATUS" | "$JQ" '.goroutines')
-            printf "syncthing_goroutine.value %s\n" "$GOROUTINES"
+            printf 'syncthing_goroutine.value %s\n' "$GOROUTINES"
     esac
 }
 
@@ -142,8 +142,8 @@ EOM
             CONNECTIONS=$("$CURL" -s -X GET -H "X-API-Key: $syncthing_apikey" "$syncthing_proto://$syncthing_host:$syncthing_port/rest/system/connections")
             IBT=$(echo "$CONNECTIONS" | "$JQ" '.total | .inBytesTotal')
             OBT=$(echo "$CONNECTIONS" | "$JQ" '.total | .outBytesTotal')
-            printf "syncthing_transfer_up.value %s\n" "$IBT"
-            printf "syncthing_transfer_down.value %s\n" "$OBT"
+            printf 'syncthing_transfer_up.value %s\n' "$IBT"
+            printf 'syncthing_transfer_down.value %s\n' "$OBT"
     esac
 }
 
diff --git a/plugins/zfs/zfs-filesystem-graph b/plugins/zfs/zfs-filesystem-graph
index 1324f95d..8bc3ca07 100755
--- a/plugins/zfs/zfs-filesystem-graph
+++ b/plugins/zfs/zfs-filesystem-graph
@@ -21,7 +21,7 @@
 # For now this plugin does not allow "_" in the name of a zpool or filesystems
 #
 
-myname=`basename $0 | sed 's/^zfs_fs_//g' | sed -e 's/_/\//g'`
+myname=$(basename "$0" | sed 's/^zfs_fs_//g' | sed -e 's/_/\//g')
 
 if [ "$1" = "autoconf" ]; then
     # Makes little sense to autoconf if you can't suggest
@@ -33,7 +33,9 @@ if [ "$1" = "suggest" ]; then
 	exit 0
 fi
 
-values=( $(zfs get -p usedbydataset,usedbychildren,usedbysnapshots,usedbyrefreservation,available,quota $myname | awk 'BEGIN {total=0;} { if( NR==1 ) next; } !/quota/ {total=total+$3;} {print $3} END{print total;}') )
+read -r -a values <<<"$(zfs get -p usedbydataset,usedbychildren,usedbysnapshots,usedbyrefreservation,available,quota "$myname" \
+    | awk 'BEGIN {total=0;} { if( NR==1 ) next; } !/quota/ {total=total+$3;} {print $3} END{print total;}')"
+
 
 if [ "$1" = "config" ]; then