diff --git a/scripts/githelper.sh b/scripts/githelper.sh
index 283192d2f13..d914960ed0d 100644
--- a/scripts/githelper.sh
+++ b/scripts/githelper.sh
@@ -1,3 +1,5 @@
+#!/bin/false
+#shellcheck disable=SC1008 
 #
 # This is a bash shell fragment, intended to be sourced by scripts that
 # want to work with git in the emc2 repo.
@@ -28,63 +30,71 @@ function githelper() {
     case $GIT_BRANCH in
         master)
             GIT_TAG_GLOB="v2.10.*"
+            # shellcheck disable=SC2034
             DEB_COMPONENT="master"
             ;;
         # release branches have names matching "number.number", which is awkward to express as a glob
         [0-9].[0-9] | [0-9].[0-9][0-9] | [0-9].[0-9][0-9][0-9] | [0-9][0-9].[0-9] | [0-9][0-9].[0-9][0-9] | [0-9][0-9].[0-9][0-9][0-9])
             GIT_TAG_GLOB="v${GIT_BRANCH}.*"
+            # shellcheck disable=SC2034
             DEB_COMPONENT=$GIT_BRANCH
             ;;
         v2.5_branch)
             GIT_TAG_GLOB="v2.5*"
+            # shellcheck disable=SC2034
             DEB_COMPONENT="v2.5_branch"
             ;;
         v2.4_branch)
             GIT_TAG_GLOB="v2.4*"
+            # shellcheck disable=SC2034
             DEB_COMPONENT="v2.4_branch"
             ;;
         *)
             GIT_TAG_GLOB="*"
+            # shellcheck disable=SC2034
             DEB_COMPONENT="scratch"
             ;;
     esac
 
 
     # use the gnupg keyring from our git repo to verify signatures on the release tags
-    export GNUPGHOME=$(git rev-parse --show-toplevel)/gnupg
+    export GNUPGHOME
+    GNUPGHOME=$(git rev-parse --show-toplevel)/gnupg
 
     NEWEST_SIGNED_TAG_UTIME=-1
     NEWEST_UNSIGNED_TAG_UTIME=-1
     for TAG in $(git tag -l "$GIT_TAG_GLOB"); do
-        if ! git cat-file tag $TAG > /dev/null 2> /dev/null; then
+        if ! git cat-file tag "$TAG" > /dev/null 2> /dev/null; then
             continue
         fi
 
-        TAG_UTIME=$(git cat-file tag $TAG | grep tagger | awk '{print $(NF-1)-$NF*36}')
+        TAG_UTIME=$(git cat-file tag "$TAG" | grep tagger | awk '{print $(NF-1)-$NF*36}')
 
         if git tag -v "$TAG" > /dev/null 2> /dev/null; then
             # it's a valid signed tag
-            if [ $TAG_UTIME -gt $NEWEST_SIGNED_TAG_UTIME ]; then
-                NEWEST_SIGNED_TAG=$TAG
-                NEWEST_SIGNED_TAG_UTIME=$TAG_UTIME
+            if [ "$TAG_UTIME" -gt "$NEWEST_SIGNED_TAG_UTIME" ]; then
+                NEWEST_SIGNED_TAG="$TAG"
+                NEWEST_SIGNED_TAG_UTIME="$TAG_UTIME"
             fi
         else
             # unsigned tag
-            if [ $TAG_UTIME -gt $NEWEST_UNSIGNED_TAG_UTIME ]; then
-                NEWEST_UNSIGNED_TAG=$TAG
-                NEWEST_UNSIGNED_TAG_UTIME=$TAG_UTIME
+            if [ "$TAG_UTIME" -gt "$NEWEST_UNSIGNED_TAG_UTIME" ]; then
+                NEWEST_UNSIGNED_TAG="$TAG"
+                NEWEST_UNSIGNED_TAG_UTIME="$TAG_UTIME"
             fi
         fi
 
     done
 
-    if [ $NEWEST_SIGNED_TAG_UTIME -gt -1 ]; then
+    if [ "$NEWEST_SIGNED_TAG_UTIME" -gt -1 ]; then
+        # shellcheck disable=SC2034
         GIT_TAG="$NEWEST_SIGNED_TAG"
         return
     fi
 
-    if [ $NEWEST_UNSIGNED_TAG_UTIME -gt -1 ]; then
+    if [ "$NEWEST_UNSIGNED_TAG_UTIME" -gt -1 ]; then
         echo "no signed tags found, falling back to unsigned tags" > /dev/null 1>&2
+        # shellcheck disable=SC2034
         GIT_TAG="$NEWEST_UNSIGNED_TAG"
         return
     fi
diff --git a/tests/build/header-sanity/test.sh b/tests/build/header-sanity/test.sh
index 38fbdf6f501..717e7f7c9f9 100755
--- a/tests/build/header-sanity/test.sh
+++ b/tests/build/header-sanity/test.sh
@@ -1,21 +1,28 @@
 #!/bin/sh
 set -xe 
 CPPFLAGS=$(pkg-config --silence-errors --cflags libtirpc)
-for i in $HEADERS/*.h; do
+
+for i in "$HEADERS"/*.h
+do
     case $i in
     */rtapi_app.h) continue ;;
     esac
+    # shellcheck disable=SC2086
     gcc ${CPPFLAGS} -DULAPI -I$HEADERS -E -x c $i > /dev/null
 done
-for i in $HEADERS/*.h $HEADERS/*.hh; do
-    case $i in
+
+for i in "$HEADERS"/*.h "$HEADERS"/*.hh
+do
+    case "$i" in
     */rtapi_app.h) continue ;;
     */interp_internal.hh) continue ;;
     esac
+    # shellcheck disable=SC2086
     if g++ ${CPPFLAGS} -std=c++11 -S -o /dev/null -xcxx /dev/null > /dev/null 2>&1; then
         ELEVEN=-std=c++11
     else
         ELEVEN=-std=c++0x
     fi
-    g++ ${CPPFLAGS} $ELEVEN -DULAPI -I$HEADERS -E -x c++ $i > /dev/null
+    # shellcheck disable=SC2086
+    g++ ${CPPFLAGS} $ELEVEN -DULAPI -I$HEADERS -E -x c++ "$i" > /dev/null
 done
diff --git a/tests/ccomp/lathe-comp/test.sh b/tests/ccomp/lathe-comp/test.sh
index b631a39327a..f74438f2b88 100644
--- a/tests/ccomp/lathe-comp/test.sh
+++ b/tests/ccomp/lathe-comp/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -t test.tbl -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/ccomp/mill-g90g91g92/test.sh b/tests/ccomp/mill-g90g91g92/test.sh
index b631a39327a..f74438f2b88 100644
--- a/tests/ccomp/mill-g90g91g92/test.sh
+++ b/tests/ccomp/mill-g90g91g92/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -t test.tbl -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/ccomp/mill-line-arc-entry/test.sh b/tests/ccomp/mill-line-arc-entry/test.sh
index b631a39327a..f74438f2b88 100644
--- a/tests/ccomp/mill-line-arc-entry/test.sh
+++ b/tests/ccomp/mill-line-arc-entry/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -t test.tbl -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/ccomp/mill-zchanges/test.sh b/tests/ccomp/mill-zchanges/test.sh
index b631a39327a..f74438f2b88 100644
--- a/tests/ccomp/mill-zchanges/test.sh
+++ b/tests/ccomp/mill-zchanges/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -t test.tbl -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/classicladder/estop/test.sh b/tests/classicladder/estop/test.sh
index 2affbde136c..fb283a41de4 100755
--- a/tests/classicladder/estop/test.sh
+++ b/tests/classicladder/estop/test.sh
@@ -7,4 +7,4 @@
 if [ "libeatmydata.so" = "$LD_PRELOAD" ] ; then
     unset LD_PRELOAD
 fi
-exec linuxcnc $(dirname $0)/classicladder-estop.ini
+exec linuxcnc "$(dirname "$0")"/classicladder-estop.ini
diff --git a/tests/halcompile/names/test.sh b/tests/halcompile/names/test.sh
index 5a997bda9fc..a1ae5e9271d 100755
--- a/tests/halcompile/names/test.sh
+++ b/tests/halcompile/names/test.sh
@@ -3,11 +3,12 @@ set -x
 
 # this one must succeed
 rm -f names_match.c
-halcompile names_match.comp
-if [ $? -ne 0 ]; then
+
+if ! halcompile names_match.comp; then
     echo 'halcompile failed to process names_match.comp'
     exit 1
 fi
+
 if [ ! -f names_match.c ]; then
     echo 'halcompile failed to produce names_match.c'
     exit 1
@@ -15,11 +16,12 @@ fi
 
 # this one must fail
 rm -f names_dont_match.c
-halcompile names_dont_match.comp
-if [ $? -eq 0 ]; then
+
+if halcompile names_dont_match.comp; then
     echo 'halcompile erroneously accepted names_dont_match.comp'
     exit 1
 fi
+
 if [ -f names_dont_match.c ]; then
     echo 'halcompile erroneously produced names_dont_match.c'
     exit 1
diff --git a/tests/hm2-idrom/test.sh b/tests/hm2-idrom/test.sh
index 8930c887f9b..316ca1c3137 100755
--- a/tests/hm2-idrom/test.sh
+++ b/tests/hm2-idrom/test.sh
@@ -19,11 +19,11 @@ Error[14]="hm2/hm2_test\.0: IDROM IOPorts is 0 but llio num_ioport_connectors is
 result=0
 
 TEST_PATTERN=0
-while [ ! -z "${Error[$TEST_PATTERN]}" ]; do
+while [ -n "${Error[$TEST_PATTERN]}" ]; do
     export TEST_PATTERN
     halrun -f broken-load-test.hal >halrun-stdout 2>halrun-stderr
     ./check-dmesg.py "${Error[$TEST_PATTERN]}" || exit $?
-    TEST_PATTERN=$(($TEST_PATTERN+1))
+    TEST_PATTERN=$((TEST_PATTERN+1))
 done
 
 exit $result
diff --git a/tests/interp/cam-nisley/test.sh b/tests/interp/cam-nisley/test.sh
index 3ee34072b1b..4440735bfae 100644
--- a/tests/interp/cam-nisley/test.sh
+++ b/tests/interp/cam-nisley/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -t test.tbl -g cam.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/crazy-paths/test.sh b/tests/interp/crazy-paths/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/interp/crazy-paths/test.sh
+++ b/tests/interp/crazy-paths/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/do-while-break/test.sh b/tests/interp/do-while-break/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/interp/do-while-break/test.sh
+++ b/tests/interp/do-while-break/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/exists/test.sh b/tests/interp/exists/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/interp/exists/test.sh
+++ b/tests/interp/exists/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/flowsnake/test.sh b/tests/interp/flowsnake/test.sh
index 68e5ed2082f..18893aab433 100644
--- a/tests/interp/flowsnake/test.sh
+++ b/tests/interp/flowsnake/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g flowsnake.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/fractional-linenumbers/test.sh b/tests/interp/fractional-linenumbers/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/interp/fractional-linenumbers/test.sh
+++ b/tests/interp/fractional-linenumbers/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g10/g10-l1-l10/test.sh b/tests/interp/g10/g10-l1-l10/test.sh
index 29ef11d7a75..52077f363e2 100755
--- a/tests/interp/g10/g10-l1-l10/test.sh
+++ b/tests/interp/g10/g10-l1-l10/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc -t test.tbl | awk '{$1=""; print}' | sed 's/-0\.0000/0.0000/g'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g10/g10-l11/test.sh b/tests/interp/g10/g10-l11/test.sh
index 29ef11d7a75..52077f363e2 100755
--- a/tests/interp/g10/g10-l11/test.sh
+++ b/tests/interp/g10/g10-l11/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc -t test.tbl | awk '{$1=""; print}' | sed 's/-0\.0000/0.0000/g'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g10/g10-l2-while-active/test.sh b/tests/interp/g10/g10-l2-while-active/test.sh
index 83d69e365c8..2afa80d1ca5 100755
--- a/tests/interp/g10/g10-l2-while-active/test.sh
+++ b/tests/interp/g10/g10-l2-while-active/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g10/g10-l20-while-active/test.sh b/tests/interp/g10/g10-l20-while-active/test.sh
index 6d4141e75aa..65bddf51a33 100755
--- a/tests/interp/g10/g10-l20-while-active/test.sh
+++ b/tests/interp/g10/g10-l20-while-active/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}' | sed 's/-0\.0000/0.0000/g'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g10/g10-with-g92/test.sh b/tests/interp/g10/g10-with-g92/test.sh
index 8fa0c30ded8..69ec8bee746 100755
--- a/tests/interp/g10/g10-with-g92/test.sh
+++ b/tests/interp/g10/g10-with-g92/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc -t test.tbl | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g33.1/test.sh b/tests/interp/g33.1/test.sh
index 5a9af07688e..574a4921f8a 100644
--- a/tests/interp/g33.1/test.sh
+++ b/tests/interp/g33.1/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g g33.1.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g6164/test.sh b/tests/interp/g6164/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/interp/g6164/test.sh
+++ b/tests/interp/g6164/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g71-endless-loop/test.sh b/tests/interp/g71-endless-loop/test.sh
index 1bd1a760d80..5394b9f3867 100755
--- a/tests/interp/g71-endless-loop/test.sh
+++ b/tests/interp/g71-endless-loop/test.sh
@@ -10,14 +10,14 @@ pid=$!
 
 # Give it 10 seconds to complete
 count=10
-while [ 0 -lt $count ] && kill -0 $pid > /dev/null 2>&1 ; do
+while [ 0 -lt "$count" ] && kill -0 "$pid" > /dev/null 2>&1 ; do
     sleep 1
-    count=$(($count - 1))
+    count=$((count - 1))
 done
 
-if kill -0 $pid > /dev/null 2>&1; then
-    kill -9 $pid
-    echo "error: g71-endless-loop.ngc program seem to be stuck, killing"
+if kill -0 "$pid" > /dev/null 2>&1; then
+    kill -9 "$pid"
+    echo "E: g71-endless-loop.ngc program seem to be stuck, killing"
     exit 1
 fi
 
diff --git a/tests/interp/g71-with-g70/test.sh b/tests/interp/g71-with-g70/test.sh
index 4b4a415b7f6..c05131005da 100755
--- a/tests/interp/g71-with-g70/test.sh
+++ b/tests/interp/g71-with-g70/test.sh
@@ -7,13 +7,13 @@ pid=$!
 
 # Give it 5 seconds to complete
 count=5
-while [ 0 -lt $count ] && kill -0 $pid > /dev/null 2>&1 ; do
+while [ 0 -lt "$count" ] && kill -0 "$pid" > /dev/null 2>&1 ; do
     sleep 1
-    count=$(($count - 1))
+    count=$((count - 1))
 done
 
-if kill -0 $pid > /dev/null 2>&1; then
-    kill -9 $pid
+if kill -0 "$pid" > /dev/null 2>&1; then
+    kill -9 "$pid"
     echo "error: g71_and_g70.ngc program seem to be stuck, killing"
     exit 1
 fi
diff --git a/tests/interp/g72-facing/test.sh b/tests/interp/g72-facing/test.sh
index dd1faa09c3d..9a50906825c 100755
--- a/tests/interp/g72-facing/test.sh
+++ b/tests/interp/g72-facing/test.sh
@@ -8,14 +8,14 @@ pid=$!
 
 # Give it 10 seconds to complete
 count=10
-while [ 0 -lt $count ] && kill -0 $pid > /dev/null 2>&1 ; do
+while [ 0 -lt "$count" ] && kill -0 "$pid" > /dev/null 2>&1 ; do
     sleep 1
-    count=$(($count - 1))
+    count=$((count - 1))
 done
 
-if kill -0 $pid > /dev/null 2>&1; then
-    kill -9 $pid
-    echo "error: g71-iterations-present.ngc program seem to be stuck, killing"
+if kill -0 "$pid" > /dev/null 2>&1; then
+    kill -9 "$pid"
+    echo "E: g71-iterations-present.ngc program seem to be stuck, killing"
     exit 1
 fi
 
diff --git a/tests/interp/g72-missing-iteration/test.sh b/tests/interp/g72-missing-iteration/test.sh
index bd67a9bd6e4..acd1d57fec7 100755
--- a/tests/interp/g72-missing-iteration/test.sh
+++ b/tests/interp/g72-missing-iteration/test.sh
@@ -10,14 +10,14 @@ pid=$!
 
 # Give it 10 seconds to complete
 count=10
-while [ 0 -lt $count ] && kill -0 $pid > /dev/null 2>&1 ; do
+while [ 0 -lt "$count" ] && kill -0 "$pid" > /dev/null 2>&1 ; do
     sleep 1
     count=$((count - 1))
 done
 
-if kill -0 $pid > /dev/null 2>&1; then
-    kill -9 $pid
-    echo "error: g71-iterations-missing.ngc program seem to be stuck, killing"
+if kill -0 "$pid" > /dev/null 2>&1; then
+    kill -9 "$pid"
+    echo "E: g71-iterations-missing.ngc program seem to be stuck, killing"
     exit 1
 fi
 
diff --git a/tests/interp/g76/test.sh b/tests/interp/g76/test.sh
index e5c98955404..1993dcb1c88 100644
--- a/tests/interp/g76/test.sh
+++ b/tests/interp/g76/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -t test.tbl -g g76only.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g81/g17/g98/test.sh b/tests/interp/g81/g17/g98/test.sh
index 3aa65b53475..214cd02540e 100644
--- a/tests/interp/g81/g17/g98/test.sh
+++ b/tests/interp/g81/g17/g98/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g g17-g98-g81.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g81/g17/g99/test.sh b/tests/interp/g81/g17/g99/test.sh
index 466c7243a0c..f4f8fec3660 100644
--- a/tests/interp/g81/g17/g99/test.sh
+++ b/tests/interp/g81/g17/g99/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g g17-g99-g81.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g81/g18/g98/test.sh b/tests/interp/g81/g18/g98/test.sh
index 8828e2e9319..056ffb5014e 100644
--- a/tests/interp/g81/g18/g98/test.sh
+++ b/tests/interp/g81/g18/g98/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g g18-g98-g81.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g81/g18/g99/test.sh b/tests/interp/g81/g18/g99/test.sh
index 4de0eb0743c..1eba671e2f8 100644
--- a/tests/interp/g81/g18/g99/test.sh
+++ b/tests/interp/g81/g18/g99/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g g18-g99-g81.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g81/g19/g98/test.sh b/tests/interp/g81/g19/g98/test.sh
index d4f14b95f46..a10d41f6953 100644
--- a/tests/interp/g81/g19/g98/test.sh
+++ b/tests/interp/g81/g19/g98/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g g19-g98-g81.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g81/g19/g99/test.sh b/tests/interp/g81/g19/g99/test.sh
index 69187669c25..ef2c0ac2ac0 100644
--- a/tests/interp/g81/g19/g99/test.sh
+++ b/tests/interp/g81/g19/g99/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g g19-g99-g81.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g84/g17/g98/test.sh b/tests/interp/g84/g17/g98/test.sh
index 601e4ada81f..5a43938a92b 100755
--- a/tests/interp/g84/g17/g98/test.sh
+++ b/tests/interp/g84/g17/g98/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g g17-g98-g84.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g84/g17/g99/test.sh b/tests/interp/g84/g17/g99/test.sh
index ab358fce49a..5b95133f8e3 100644
--- a/tests/interp/g84/g17/g99/test.sh
+++ b/tests/interp/g84/g17/g99/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g g17-g99-g84.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g84/g18/g98/test.sh b/tests/interp/g84/g18/g98/test.sh
index 9110de97652..0b60af3801d 100644
--- a/tests/interp/g84/g18/g98/test.sh
+++ b/tests/interp/g84/g18/g98/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g g18-g98-g84.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g84/g18/g99/test.sh b/tests/interp/g84/g18/g99/test.sh
index b7008b70fb0..f946371d20e 100644
--- a/tests/interp/g84/g18/g99/test.sh
+++ b/tests/interp/g84/g18/g99/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g g18-g99-g84.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g84/g19/g98/test.sh b/tests/interp/g84/g19/g98/test.sh
index 9b0806ee414..4545239caee 100644
--- a/tests/interp/g84/g19/g98/test.sh
+++ b/tests/interp/g84/g19/g98/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g g19-g98-g84.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/g84/g19/g99/test.sh b/tests/interp/g84/g19/g99/test.sh
index 16e5a42673a..e82c38e1084 100644
--- a/tests/interp/g84/g19/g99/test.sh
+++ b/tests/interp/g84/g19/g99/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g g19-g99-g84.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/iniparam-failassign/test.sh b/tests/interp/iniparam-failassign/test.sh
index af88e94afae..f15a7afbf8a 100755
--- a/tests/interp/iniparam-failassign/test.sh
+++ b/tests/interp/iniparam-failassign/test.sh
@@ -1,10 +1,8 @@
 #!/bin/bash
 export PYTHONUNBUFFERED=1
-rs274 -i test.ini  -g test.ngc 2>&1
-
-# expected to fail
-if [ $? -ne 0 ]; then
+if ! rs274 -i test.ini  -g test.ngc 2>&1
+then
+    # expected to fail
     exit 0
 fi
-
 exit 1
diff --git a/tests/interp/inside-corners/test.sh b/tests/interp/inside-corners/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/interp/inside-corners/test.sh
+++ b/tests/interp/inside-corners/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/inverse-time-with-comp/test.sh b/tests/interp/inverse-time-with-comp/test.sh
index 9279a98e2f2..cec720fe1f7 100644
--- a/tests/interp/inverse-time-with-comp/test.sh
+++ b/tests/interp/inverse-time-with-comp/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g inverse.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/m19/test.sh b/tests/interp/m19/test.sh
index da351514599..22f60fd0ac7 100644
--- a/tests/interp/m19/test.sh
+++ b/tests/interp/m19/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -n 0 -i test.ini -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/m98m99/01-basics/test.sh b/tests/interp/m98m99/01-basics/test.sh
index 83d69e365c8..2afa80d1ca5 100755
--- a/tests/interp/m98m99/01-basics/test.sh
+++ b/tests/interp/m98m99/01-basics/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/m98m99/02-variables/test.sh b/tests/interp/m98m99/02-variables/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/interp/m98m99/02-variables/test.sh
+++ b/tests/interp/m98m99/02-variables/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/m98m99/03-error-M98-no-P-word/test.sh b/tests/interp/m98m99/03-error-M98-no-P-word/test.sh
index a0d94f6194c..4905af41aa2 100755
--- a/tests/interp/m98m99/03-error-M98-no-P-word/test.sh
+++ b/tests/interp/m98m99/03-error-M98-no-P-word/test.sh
@@ -1,9 +1,7 @@
 #!/bin/bash
-rs274  -g test.ngc 2>&1
-
-# expected to fail
-if [ $? -ne 0 ]; then
+if ! rs274  -g test.ngc 2>&1
+then
+    # expected to fail
     exit 0
 fi
-
 exit 1
diff --git a/tests/interp/m98m99/05-M98-loops/test.sh b/tests/interp/m98m99/05-M98-loops/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/interp/m98m99/05-M98-loops/test.sh
+++ b/tests/interp/m98m99/05-M98-loops/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/m98m99/07-nested-subs/test.sh b/tests/interp/m98m99/07-nested-subs/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/interp/m98m99/07-nested-subs/test.sh
+++ b/tests/interp/m98m99/07-nested-subs/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/m98m99/08-sub-follows-main/test.sh b/tests/interp/m98m99/08-sub-follows-main/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/interp/m98m99/08-sub-follows-main/test.sh
+++ b/tests/interp/m98m99/08-sub-follows-main/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/m98m99/10-M98-P001/test.sh b/tests/interp/m98m99/10-M98-P001/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/interp/m98m99/10-M98-P001/test.sh
+++ b/tests/interp/m98m99/10-M98-P001/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/m98m99/11-main-program-oword/test.sh b/tests/interp/m98m99/11-main-program-oword/test.sh
index 448dc119130..ce5ae835cd6 100644
--- a/tests/interp/m98m99/11-main-program-oword/test.sh
+++ b/tests/interp/m98m99/11-main-program-oword/test.sh
@@ -18,8 +18,8 @@ ILLEGAL_TESTS="
 #
 for t in $LEGAL_TESTS; do
     echo "Legal test ${t}:"
-    rs274 -g test-legal-${t}.ngc | awk '{$1=""; print}'
-    res=${PIPESTATUS[0]}
+    rs274 -g "test-legal-${t}.ngc" | awk '{$1=""; print}'
+    res="${PIPESTATUS[0]}"
     if test "$res" = 0; then
 	echo "Success: Test '${t}' exited ${res}" >&2
     else
@@ -33,8 +33,8 @@ done
 for t in $ILLEGAL_TESTS; do
     echo "Illegal test ${t}:"
     res=-1
-    rs274 -g test-illegal-${t}.ngc | awk '{$1=""; print}'
-    res=${PIPESTATUS[0]}
+    rs274 -g "test-illegal-${t}.ngc" | awk '{$1=""; print}'
+    res="${PIPESTATUS[0]}"
     if test "$res" = 0; then
 	echo "Error: Illegal test '${t}' exited ${res}" >&2
 	exit "$res"
diff --git a/tests/interp/m98m99/12-M99-endless-main-program/test.sh b/tests/interp/m98m99/12-M99-endless-main-program/test.sh
index 9a0ef1271f3..7ef57534546 100755
--- a/tests/interp/m98m99/12-M99-endless-main-program/test.sh
+++ b/tests/interp/m98m99/12-M99-endless-main-program/test.sh
@@ -7,4 +7,4 @@ linuxcnc -r motion-logger.ini
 
 # Run test file in stand-alone interpreter:  should run program once
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/magic_comments/param_format_printing/test.sh b/tests/interp/magic_comments/param_format_printing/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/interp/magic_comments/param_format_printing/test.sh
+++ b/tests/interp/magic_comments/param_format_printing/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/namedparam-bug424/test.sh b/tests/interp/namedparam-bug424/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/interp/namedparam-bug424/test.sh
+++ b/tests/interp/namedparam-bug424/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/oword-bug315-p2/test.sh b/tests/interp/oword-bug315-p2/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/interp/oword-bug315-p2/test.sh
+++ b/tests/interp/oword-bug315-p2/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/oword-bug315/test.sh b/tests/interp/oword-bug315/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/interp/oword-bug315/test.sh
+++ b/tests/interp/oword-bug315/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/oword-unwind/test.sh b/tests/interp/oword-unwind/test.sh
index da351514599..22f60fd0ac7 100644
--- a/tests/interp/oword-unwind/test.sh
+++ b/tests/interp/oword-unwind/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -n 0 -i test.ini -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/plug/absolute/test.sh b/tests/interp/plug/absolute/test.sh
index 7d29952328b..7044c07bf33 100644
--- a/tests/interp/plug/absolute/test.sh
+++ b/tests/interp/plug/absolute/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -p "${LIBDIR}"/linuxcnc/canterp.so -g canon | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/plug/filename/test.sh b/tests/interp/plug/filename/test.sh
index 40043f9edd3..e6c1a20e9a4 100644
--- a/tests/interp/plug/filename/test.sh
+++ b/tests/interp/plug/filename/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -p canterp.so -g canon | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/plug/relative/test.sh b/tests/interp/plug/relative/test.sh
index defb33cfdb0..55db7ddb4b5 100644
--- a/tests/interp/plug/relative/test.sh
+++ b/tests/interp/plug/relative/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -p ./canterp.so -g canon | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/return-value/test.sh b/tests/interp/return-value/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/interp/return-value/test.sh
+++ b/tests/interp/return-value/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/rotation/abs-pts/test.sh b/tests/interp/rotation/abs-pts/test.sh
index 5b214441322..53e9013752c 100644
--- a/tests/interp/rotation/abs-pts/test.sh
+++ b/tests/interp/rotation/abs-pts/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc -t test.tbl | awk '/MESSAGE/ {$1=""; print}' | sed 's/-0\.0000/0.0000/g'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/rotation/g28/test.sh b/tests/interp/rotation/g28/test.sh
index 33218bea6ab..998595ed67e 100755
--- a/tests/interp/rotation/g28/test.sh
+++ b/tests/interp/rotation/g28/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g g28.ngc | sed 's/-0\.0000/0.0000/g'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/rotation/g53/test.sh b/tests/interp/rotation/g53/test.sh
index ac5b7fe17a5..8ced2f78e4b 100755
--- a/tests/interp/rotation/g53/test.sh
+++ b/tests/interp/rotation/g53/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g g53.ngc | sed 's/-0\.0000/0.0000/g'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/interp/subs-follow-main/test.sh b/tests/interp/subs-follow-main/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/interp/subs-follow-main/test.sh
+++ b/tests/interp/subs-follow-main/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/linuxcncrsh-tcp/test.sh b/tests/linuxcncrsh-tcp/test.sh
index a8da4840ac4..218cff9d9ba 100755
--- a/tests/linuxcncrsh-tcp/test.sh
+++ b/tests/linuxcncrsh-tcp/test.sh
@@ -12,42 +12,42 @@ linuxcnc -r linuxcncrsh-test.ini &
 
 # let linuxcnc come up
 TOGO=80
-while [  $TOGO -gt 0 ]; do
+while [ "$TOGO" -gt 0 ]; do
     echo trying to connect to linuxcncrsh TOGO=$TOGO
     if nc -z localhost 5007; then
         break
     fi
     sleep 0.25
-    TOGO=$(($TOGO - 1))
+    TOGO=$((TOGO - 1))
 done
-if [  $TOGO -eq 0 ]; then
-    echo connection to linuxcncrsh timed out
+if [  "$TOGO" -eq 0 ]; then
+    echo "connection to linuxcncrsh timed out"
     exit 1
 fi
 
 
 (
-    echo hello EMC mt 1.0
-    echo set enable EMCTOO
+    echo "hello EMC mt 1.0"
+    echo "set enable EMCTOO"
 
     # ask linuxcncrsh to not read the next command until it's done running
     # the current one
-    echo set set_wait done
+    echo "set set_wait done"
 
-    echo set mode manual
-    echo set estop off
-    echo set machine on
+    echo "set mode manual"
+    echo "set estop off"
+    echo "set machine on"
 
-    echo set mode mdi
-    echo set mdi m100 p-1 q-2
+    echo "set mode mdi"
+    echo "set mdi m100 p-1 q-2"
     sleep 1
 
     # here comes a big blob
     dd bs=4096 if=lots-of-gcode
 
-    echo set mdi m100 p-3 q-4
+    echo "set mdi m100 p-3 q-4"
 
-    echo shutdown
+    echo "shutdown"
 ) | nc localhost 5007
 
 
diff --git a/tests/lowlevel/mutex/test.sh b/tests/lowlevel/mutex/test.sh
index 9c6afff1754..f4eb03c34b8 100755
--- a/tests/lowlevel/mutex/test.sh
+++ b/tests/lowlevel/mutex/test.sh
@@ -1,4 +1,5 @@
 #!/bin/sh
+# shellcheck disable=SC2086
 gcc -O -I${HEADERS} test.c -o test -DULAPI -std=gnu99 -pthread || exit 1
 ./test; exitval=$?
 rm -f test
diff --git a/tests/m70-m73/m70m72-restore.0/test.sh b/tests/m70-m73/m70m72-restore.0/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/m70-m73/m70m72-restore.0/test.sh
+++ b/tests/m70-m73/m70m72-restore.0/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/m70-m73/m73-flood-mist-restore.0/test.sh b/tests/m70-m73/m73-flood-mist-restore.0/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/m70-m73/m73-flood-mist-restore.0/test.sh
+++ b/tests/m70-m73/m73-flood-mist-restore.0/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/m70-m73/m73autorestore.0/test.sh b/tests/m70-m73/m73autorestore.0/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/m70-m73/m73autorestore.0/test.sh
+++ b/tests/m70-m73/m73autorestore.0/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/mdi-queue/oword-queue-buster/test.sh b/tests/mdi-queue/oword-queue-buster/test.sh
index b52b2bac433..344b03d0450 100755
--- a/tests/mdi-queue/oword-queue-buster/test.sh
+++ b/tests/mdi-queue/oword-queue-buster/test.sh
@@ -28,9 +28,9 @@ while [  $TOGO -gt 0 ]; do
         break
     fi
     sleep 0.25
-    TOGO=$(($TOGO - 1))
+    TOGO=$((TOGO - 1))
 done
-if [  $TOGO -eq 0 ]; then
+if [ "$TOGO" -eq 0 ]; then
     echo "E: connection to linuxcncrsh timed out"
     exit 1
 fi
@@ -42,12 +42,13 @@ NUM_MDIS=1
 NUM_MDIS_LEFT=$NUM_MDIS
 TOOL=1
 for i in $(seq 0 1000); do
-    NUM_MDIS_LEFT=$(($NUM_MDIS_LEFT - 1))
+    NUM_MDIS_LEFT=$((NUM_MDIS_LEFT - 1))
     if [ $NUM_MDIS_LEFT -eq 0 ]; then
         echo "set mdi o<queue-buster> call [$TOOL]" >> lots-of-gcode
+        # shellcheck disable=SC2129
         echo "P is 12345.000000" >> expected-gcode-output
-        echo "P is $((-1 * $TOOL)).000000" >> expected-gcode-output
-        echo "P is 54321.000000"  >> expected-gcode-output
+        echo "P is $((-1 * TOOL)).000000" >> expected-gcode-output
+        echo "P is 54321.000000" >> expected-gcode-output
 
         if [ $TOOL -eq 1 ]; then
             TOOL=2
@@ -55,8 +56,8 @@ for i in $(seq 0 1000); do
             TOOL=1
         fi
 
-        NUM_MDIS=$(($NUM_MDIS + 1))
-        if [ $NUM_MDIS -gt 10 ]; then
+        NUM_MDIS=$((NUM_MDIS + 1))
+        if [ "$NUM_MDIS" -gt 10 ]; then
             NUM_MDIS=1
         fi
 
@@ -68,27 +69,27 @@ done
 echo "P is -200.000000" >> expected-gcode-output
 
 (
-    echo hello EMC mt 1.0
-    echo set enable EMCTOO
+    echo "hello EMC mt 1.0"
+    echo "set enable EMCTOO"
 
-    echo set mode manual
-    echo set estop off
-    echo set machine on
+    echo "set mode manual"
+    echo "set estop off"
+    echo "set machine on"
 
-    echo set mode auto
-    echo set open dummy.ngc
+    echo "set mode auto"
+    echo "set open dummy.ngc"
 
-    echo set mode mdi
-    echo set mdi m100 p-100
-    echo set wait done
+    echo "set mode mdi"
+    echo "set mdi m100 p-100"
+    echo "set wait done"
 
     # here comes a big blob
     dd bs=4096 if=lots-of-gcode
 
-    echo set mdi m100 p-200
-    echo set wait done
+    echo "set mdi m100 p-200"
+    echo "set wait done"
 
-    echo shutdown
+    echo "shutdown"
 ) | nc localhost 5007
 
 
diff --git a/tests/mdi-queue/simple-queue-buster/test.sh b/tests/mdi-queue/simple-queue-buster/test.sh
index 41dfcc604a0..aaa77135bca 100755
--- a/tests/mdi-queue/simple-queue-buster/test.sh
+++ b/tests/mdi-queue/simple-queue-buster/test.sh
@@ -28,7 +28,7 @@ while [  $TOGO -gt 0 ]; do
         break
     fi
     sleep 0.25
-    TOGO=$(($TOGO - 1))
+    TOGO=$((TOGO - 1))
 done
 if [  $TOGO -eq 0 ]; then
     echo connection to linuxcncrsh timed out
@@ -42,8 +42,8 @@ NUM_MDIS=1
 NUM_MDIS_LEFT=$NUM_MDIS
 TOOL=1
 for i in $(seq 0 1000); do
-    NUM_MDIS_LEFT=$(($NUM_MDIS_LEFT - 1))
-    if [ $NUM_MDIS_LEFT -eq 0 ]; then
+    NUM_MDIS_LEFT=$((NUM_MDIS_LEFT - 1))
+    if [ "$NUM_MDIS_LEFT" -eq 0 ]; then
         echo "set mdi t$TOOL m6" >> lots-of-gcode
         if [ $TOOL -eq 1 ]; then
             TOOL=2
@@ -51,8 +51,8 @@ for i in $(seq 0 1000); do
             TOOL=1
         fi
 
-        NUM_MDIS=$(($NUM_MDIS + 1))
-        if [ $NUM_MDIS -gt 10 ]; then
+        NUM_MDIS=$((NUM_MDIS + 1))
+        if [ "$NUM_MDIS" -gt 10 ]; then
             NUM_MDIS=1
         fi
 
@@ -64,28 +64,28 @@ done
 echo "P is -2.000000" >> expected-gcode-output
 
 (
-    echo hello EMC mt 1.0
-    echo set enable EMCTOO
+    echo "hello EMC mt 1.0"
+    echo "set enable EMCTOO"
 
     # ask linuxcncrsh to not read the next command until it's done running
     # the current one
-    #echo set set_wait done
+    #echo "set set_wait done"
 
-    echo set mode manual
-    echo set estop off
-    echo set machine on
+    echo "set mode manual"
+    echo "set estop off"
+    echo "set machine on"
 
-    echo set mode mdi
-    echo set mdi m100 p-1
-    echo set wait done
+    echo "set mode mdi"
+    echo "set mdi m100 p-1"
+    echo "set wait done"
 
     # here comes a big blob
     dd bs=4096 if=lots-of-gcode
 
-    echo set mdi m100 p-2
-    echo set wait done
+    echo "set mdi m100 p-2"
+    echo "set wait done"
 
-    echo shutdown
+    echo "shutdown"
 ) | nc localhost 5007
 
 
diff --git a/tests/mdi-while-queuebuster-waitflag/test.sh b/tests/mdi-while-queuebuster-waitflag/test.sh
index c010db9322e..dd204d29e10 100755
--- a/tests/mdi-while-queuebuster-waitflag/test.sh
+++ b/tests/mdi-while-queuebuster-waitflag/test.sh
@@ -1,8 +1,10 @@
 #!/bin/bash -e
 
-for i in `seq 20`; do
+# shellcheck disable=SC2034
+for i in $(seq 20)
+do
     linuxcnc -r test.ini
     if grep -q '^[^+].*Segmentation fault' stderr; then
-	exit 1
+        exit 1
     fi
 done
diff --git a/tests/module-loading/shared-test.sh b/tests/module-loading/shared-test.sh
index 4f5780138b4..645fedb7b09 100644
--- a/tests/module-loading/shared-test.sh
+++ b/tests/module-loading/shared-test.sh
@@ -3,13 +3,14 @@
 halrun setup.hal > hal-output 2>&1
 RESULT=$?
 
-NUM_PINS=$(cat hal-output | grep -E $(cat PIN_NAME_REGEX) | wc -l)
+# grep -c counts number of matches
+NUM_PINS=$(grep -E -c "$(cat PIN_NAME_REGEX)" hal-output)
 
-if [ $RESULT -ne $(cat RESULT) ]; then
+if [ "$RESULT" -ne "$(cat RESULT)" ]; then
     exit 1
 fi
 
-if [ "$NUM_PINS" -ne $(cat NUM_PINS) ]; then
+if [ "$NUM_PINS" -ne "$(cat NUM_PINS)" ]; then
     exit 1
 fi
 
diff --git a/tests/motion/g0/test.sh b/tests/motion/g0/test.sh
index b54482c459d..9d9de2bb432 100755
--- a/tests/motion/g0/test.sh
+++ b/tests/motion/g0/test.sh
@@ -7,15 +7,15 @@ wait_for_pin() {
     pin="$1"
     value="$2"
     maxwait=10 # seconds
-    while [ 0 -lt $maxwait ] \
-      && [ "$value" != "$(halcmd -s show pin $pin | awk '{print $4}')" ]; do
+    while [ 0 -lt "$maxwait" ] \
+      && [ "$value" != "$(halcmd -s show pin "$pin" | awk '{print $4}')" ]; do
         sleep 1
-	maxwait=$(($maxwait -1))
+	maxwait=$((maxwait - 1))
     done
-    if [ 0 -eq $maxwait ] ; then
-	echo "error: waiting for pin $pin timed out"
-	kill $linuxcncpid
-	kill $samplerpid
+    if [ 0 -eq "$maxwait" ] ; then
+	echo "error: waiting for pin '$pin' timed out"
+	kill "$linuxcncpid"
+	kill "$samplerpid"
 	exit 1
     fi
 }
@@ -25,47 +25,47 @@ linuxcncpid=$!
 
 # let linuxcnc come up
 TOGO=80
-while [  $TOGO -gt 0 ]; do
-    echo trying to connect to linuxcncrsh TOGO=$TOGO
+while [ "$TOGO" -gt 0 ]; do
+    echo "I: trying to connect to linuxcncrsh TOGO=$TOGO"
     if nc -z localhost 5007; then
         break
     fi
     sleep 0.25
-    TOGO=$(($TOGO - 1))
+    TOGO=$((TOGO - 1))
 done
-if [  $TOGO -eq 0 ]; then
-    echo connection to linuxcncrsh timed out
+if [ "$TOGO" -eq 0 ]; then
+    echo "E: connection to linuxcncrsh timed out"
     exit 1
 fi
 
 wait_for_pin motion.in-position TRUE
 
-echo starting to capture data
+echo "I: starting to capture data"
 halsampler -t >| result.halsamples &
 samplerpid=$!
 
 (
-    echo hello EMC mt 1.0
-    echo set enable EMCTOO
+    echo "hello EMC mt 1.0"
+    echo "set enable EMCTOO"
 
-    echo set estop off
-    echo set machine on
+    echo "set estop off"
+    echo "set machine on"
 
-    echo set mode mdi
+    echo "set mode mdi"
     dist=1
-    echo set mdi g0x$dist
+    echo "set mdi g0x$dist"
 
     # Wait for movement to complete
     wait_for_pin joint.0.pos-fb $dist
     wait_for_pin joint.0.in-position TRUE
     wait_for_pin joint.1.in-position TRUE
 
-    echo shutdown
+    echo "shutdown"
 ) | nc localhost 5007
 
 kill $samplerpid
 wait $samplerpid
-echo finished capturing data
+echo "I: finished capturing data"
 
 # wait for linuxcnc to finish
 wait $linuxcncpid
diff --git a/tests/overrun/test.sh b/tests/overrun/test.sh
index 1ef9372048f..a5fbe0ac39a 100755
--- a/tests/overrun/test.sh
+++ b/tests/overrun/test.sh
@@ -1,8 +1,9 @@
 #!/bin/sh
-TMPDIR=`mktemp -d /tmp/overrun.XXXXXX`
-trap "rm -rf $TMPDIR" 0 1 2 3 9 15
+TMPDIR=$(mktemp -d /tmp/overrun.XXXXXX)
+trap "rm -rf '$TMPDIR'" 0 1 2 3 15
+# not trapping 9 since it cannot be trapped
 
-TEST_HAL=$TMPDIR/test.hal
-echo loadusr -w echo overrun > $TMPDIR/test.hal
+TEST_HAL="$TMPDIR"/test.hal
+echo loadusr -w echo overrun > "$TMPDIR"/test.hal
 
-! $RUNTESTS $TMPDIR 2>&1
+! $RUNTESTS "$TMPDIR" 2>&1
diff --git a/tests/oword/sub.0/test.sh b/tests/oword/sub.0/test.sh
index 83d69e365c8..2afa80d1ca5 100644
--- a/tests/oword/sub.0/test.sh
+++ b/tests/oword/sub.0/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/oword/while.0/test.sh b/tests/oword/while.0/test.sh
index 83d69e365c8..2afa80d1ca5 100755
--- a/tests/oword/while.0/test.sh
+++ b/tests/oword/while.0/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/remap/duplicate-o-word/test.sh b/tests/remap/duplicate-o-word/test.sh
index 13adf7d5cf6..99269de600c 100755
--- a/tests/remap/duplicate-o-word/test.sh
+++ b/tests/remap/duplicate-o-word/test.sh
@@ -1,4 +1,4 @@
 #!/bin/bash
 export INI_FILE_NAME=test.ini
-rs274 -i $INI_FILE_NAME -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+rs274 -i "$INI_FILE_NAME" -g test.ngc | awk '{$1=""; print}'
+exit "${PIPESTATUS[0]}"
diff --git a/tests/remap/fail/args.0/test.sh b/tests/remap/fail/args.0/test.sh
index 65d4d349dfe..bb2a78ea3d5 100755
--- a/tests/remap/fail/args.0/test.sh
+++ b/tests/remap/fail/args.0/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -i test.ini -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/remap/fail/args.1/test.sh b/tests/remap/fail/args.1/test.sh
index 77a112a15ca..974f6975c31 100755
--- a/tests/remap/fail/args.1/test.sh
+++ b/tests/remap/fail/args.1/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -i test.ini -n 0 -g test.ngc 2>&1
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/remap/fail/args.2/test.sh b/tests/remap/fail/args.2/test.sh
index 77a112a15ca..974f6975c31 100755
--- a/tests/remap/fail/args.2/test.sh
+++ b/tests/remap/fail/args.2/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -i test.ini -n 0 -g test.ngc 2>&1
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/remap/fail/body-ngc/test.sh b/tests/remap/fail/body-ngc/test.sh
index 77a112a15ca..974f6975c31 100755
--- a/tests/remap/fail/body-ngc/test.sh
+++ b/tests/remap/fail/body-ngc/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -i test.ini -n 0 -g test.ngc 2>&1
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/remap/m30-interaction/test.sh b/tests/remap/m30-interaction/test.sh
index 57e28aba8d2..a3af97b0369 100755
--- a/tests/remap/m30-interaction/test.sh
+++ b/tests/remap/m30-interaction/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -i test.ini -g test.ngc 2>&1 | sed 's/^ *[0-9]* //'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/remap/nested-remaps-oword/test.sh b/tests/remap/nested-remaps-oword/test.sh
index 21d662fe18f..57cd866be11 100755
--- a/tests/remap/nested-remaps-oword/test.sh
+++ b/tests/remap/nested-remaps-oword/test.sh
@@ -1,4 +1,4 @@
 #!/bin/bash
 rs274 -i test.ini -g test.ngc 2>&1 | sed 's/^ *[0-9]* //'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
 
diff --git a/tests/remap/posargs.0/test.sh b/tests/remap/posargs.0/test.sh
index 087b90d47b6..c4f19fb4f54 100755
--- a/tests/remap/posargs.0/test.sh
+++ b/tests/remap/posargs.0/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash
 rs274 -i test.ini -n 0 -g test.ngc| awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/remap/remap-reentry/test.sh b/tests/remap/remap-reentry/test.sh
index 02f782fcdd5..2e101d82b63 100755
--- a/tests/remap/remap-reentry/test.sh
+++ b/tests/remap/remap-reentry/test.sh
@@ -1,3 +1,3 @@
 #!/bin/bash -e
 rs274 -g -i test.ini test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/remap/sequencing/test.sh b/tests/remap/sequencing/test.sh
index 13adf7d5cf6..37a5e36f0a5 100755
--- a/tests/remap/sequencing/test.sh
+++ b/tests/remap/sequencing/test.sh
@@ -1,4 +1,4 @@
 #!/bin/bash
 export INI_FILE_NAME=test.ini
 rs274 -i $INI_FILE_NAME -g test.ngc | awk '{$1=""; print}'
-exit ${PIPESTATUS[0]}
+exit "${PIPESTATUS[0]}"
diff --git a/tests/t0/shared-test.sh b/tests/t0/shared-test.sh
index c2f4b67176b..f0cd5293fe5 100644
--- a/tests/t0/shared-test.sh
+++ b/tests/t0/shared-test.sh
@@ -25,7 +25,7 @@ while [  $TOGO -gt 0 ]; do
         break
     fi
     sleep 0.25
-    TOGO=$(($TOGO - 1))
+    TOGO=$((TOGO - 1))
 done
 if [  $TOGO -eq 0 ]; then
     echo connection to linuxcncrsh timed out
diff --git a/tests/toolchanger/toolno-pocket-differ/shared-test.sh b/tests/toolchanger/toolno-pocket-differ/shared-test.sh
index 34426e36e4c..4981d739255 100755
--- a/tests/toolchanger/toolno-pocket-differ/shared-test.sh
+++ b/tests/toolchanger/toolno-pocket-differ/shared-test.sh
@@ -19,13 +19,13 @@ linuxcnc -r sim.ini &
 
 # let linuxcnc come up
 TOGO=80
-while [  $TOGO -gt 0 ]; do
+while [ "$TOGO" -gt 0 ]; do
     echo trying to connect to linuxcncrsh TOGO=$TOGO
     if nc -z localhost 5007; then
         break
     fi
     sleep 0.25
-    TOGO=$(($TOGO - 1))
+    TOGO=$((TOGO - 1))
 done
 if [  $TOGO -eq 0 ]; then
     echo connection to linuxcncrsh timed out
@@ -37,123 +37,118 @@ fi
     function introspect() {
         SEQUENCE_NUMBER=$1
         echo "set mdi m100 P6 Q$SEQUENCE_NUMBER"  # sequence number
-        echo 'set mdi m100 P0 Q#5420'             # X
-        echo 'set mdi m100 P1 Q#5421'             # Y
-        echo 'set mdi m100 P2 Q#5422'             # Z
-        echo 'set mdi m100 P3 Q#5400'             # toolno
-        echo 'set mdi m100 P4 Q#5403'             # TLO z
-        echo 'set mdi m100 P5'                    # blank line
+        echo "set mdi m100 P0 Q#5420"             # X
+        echo "set mdi m100 P1 Q#5421"             # Y
+        echo "set mdi m100 P2 Q#5422"             # Z
+        echo "set mdi m100 P3 Q#5400"             # toolno
+        echo "set mdi m100 P4 Q#5403"             # TLO z
+        echo "set mdi m100 P5"                    # blank line
     }
 
-    echo hello EMC mt 1.0
-    echo set enable EMCTOO
+    echo "hello EMC mt 1.0"
+    echo "set enable EMCTOO"
 
-    echo set estop off
-    echo set machine on
-    echo set mode mdi
+    echo "set estop off"
+    echo "set machine on"
+    echo "set mode mdi"
 
     introspect 0
 
-    echo set mdi t1 m6
+    echo "set mdi t1 m6"
     introspect 1
 
-    echo set mdi g43
+    echo "set mdi g43"
     introspect 2
 
-    echo set mdi g10 l10 p1 z.1
+    echo "set mdi g10 l10 p1 z.1"
     introspect 3
 
-    echo set mdi g43
+    echo "set mdi g43"
     introspect 4
 
-    echo set mdi g10 l10 p10 z.15
+    echo "set mdi g10 l10 p10 z.15"
     introspect 5
 
-    echo set mdi g43
+    echo "set mdi g43"
     introspect 6
 
-    echo set mdi g10 l10 p99999 z.2
+    echo "set mdi g10 l10 p99999 z.2"
     introspect 7
 
-    echo set mdi g43
+    echo "set mdi g43"
     introspect 8
 
-
-    echo set mdi t10 m6
+    echo "set mdi t10 m6"
     introspect 9
 
-    echo set mdi g43
+    echo "set mdi g43"
     introspect 10
 
-    echo set mdi g10 l10 p1 z.103
+    echo "set mdi g10 l10 p1 z.103"
     introspect 11
 
-    echo set mdi g43
+    echo "set mdi g43"
     introspect 12
 
-    echo set mdi g10 l10 p10 z.1035
+    echo "set mdi g10 l10 p10 z.1035"
     introspect 13
 
-    echo set mdi g43
+    echo "set mdi g43"
     introspect 14
 
-    echo set mdi g10 l10 p99999 z.104
+    echo "set mdi g10 l10 p99999 z.104"
     introspect 15
 
-    echo set mdi g43
+    echo "set mdi g43"
     introspect 16
 
-
-    echo set mdi t99999 m6
+    echo "set mdi t99999 m6"
     introspect 17
 
-    echo set mdi g43
+    echo "set mdi g43"
     introspect 18
 
-    echo set mdi g10 l10 p1 z.3
+    echo "set mdi g10 l10 p1 z.3"
     introspect 19
 
-    echo set mdi g43
+    echo "set mdi g43"
     introspect 20
 
-    echo set mdi g10 l10 p10 z.35
+    echo "set mdi g10 l10 p10 z.35"
     introspect 21
 
-    echo set mdi g43
+    echo "set mdi g43"
     introspect 22
 
-    echo set mdi g10 l10 p99999 z.4
+    echo "set mdi g10 l10 p99999 z.4"
     introspect 23
 
-    echo set mdi g43
+    echo "set mdi g43"
     introspect 24
 
-
-    echo set mdi t1 m6
+    echo "set mdi t1 m6"
     introspect 25
 
-    echo set mdi g43
+    echo "set mdi g43"
     introspect 26
 
-
-    echo set mdi t10 m6
+    echo "set mdi t10 m6"
     introspect 27
 
-    echo set mdi g43
+    echo "set mdi g43"
     introspect 28
 
-
-    echo set mdi t99999 m6
+    echo "set mdi t99999 m6"
     introspect 29
 
-    echo set mdi g43
+    echo "set mdi g43"
     introspect 30
 
 
     # wait for linuxcnc to finish
-    echo set wait done
+    echo "set wait done"
 
-    echo shutdown
+    echo "shutdown"
 ) | nc localhost 5007
 
 
diff --git a/tests/tooledit/test.sh b/tests/tooledit/test.sh
index bf8ef83a6b5..461d488138b 100755
--- a/tests/tooledit/test.sh
+++ b/tests/tooledit/test.sh
@@ -1,8 +1,9 @@
 #!/bin/bash
+
 # test if floating point numbers are formatted correctly
 
 if ! command -v xvfb-run &> /dev/null; then
-    echo "xvfb-run could not be found, we assume everything works" > /dev/stderr
+    echo "W: xvfb-run could not be found, we assume everything works" > /dev/stderr
     cat expected
     exit 0
 fi
@@ -11,20 +12,20 @@ fi
 #create temporary files so we don't write into write access problems
 infile=$(mktemp)
 outfile=$(mktemp)
-cat test.tbl > $infile
+cat test.tbl > "$infile"
 
 # run the test
-xvfb-run ${LINUXCNC_EMCSH/wish/tclsh} test.tcl $infile $outfile 2> tclerror.log;
+xvfb-run "${LINUXCNC_EMCSH/wish/tclsh}" test.tcl "$infile" "$outfile" 2> tclerror.log
 
-if [ $(cat tclerror.log | wc -l) -ne 0 ]; then
+if [ "$(wc -l tclerror.log)" -ne 0 ]; then
     cat tclerror.log
     exit 1
 fi
 
 # write the resulting tool table to stdout so the test framework can evaluate it
-cat $outfile
+cat "$outfile"
 
 # remove the temporary files
-rm $infile $outfile $outfile".bak"
+rm "$infile" "$outfile" "$outfile.bak"
 
 exit 0
diff --git a/tests/trajectory-planner/circular-arcs/test-lengths.sh b/tests/trajectory-planner/circular-arcs/test-lengths.sh
index 893f1e01baa..7611afd25d8 100755
--- a/tests/trajectory-planner/circular-arcs/test-lengths.sh
+++ b/tests/trajectory-planner/circular-arcs/test-lengths.sh
@@ -2,8 +2,8 @@
 set -o monitor
 ./build-debug.sh
 cp position.blank position.txt
-linuxcnc $1 > test.log &
-./machine_setup.py $2
+linuxcnc "$1" > test.log &
+./machine_setup.py "$2"
 fg
 ./save_lengths.sh test.log
 #if [ -a length_data.log ] 
diff --git a/tests/trajectory-planner/circular-arcs/test-optimization.sh b/tests/trajectory-planner/circular-arcs/test-optimization.sh
index 57fddb45908..5e54c970aaf 100755
--- a/tests/trajectory-planner/circular-arcs/test-optimization.sh
+++ b/tests/trajectory-planner/circular-arcs/test-optimization.sh
@@ -13,4 +13,4 @@ linuxcnc -r circular_arcs.ini > test.log &
 ./machine_setup.py "$1" && say_done
 fg
 ./save_activate.sh test.log
-exit $1
+exit "$1"
diff --git a/tests/trajectory-planner/circular-arcs/util/save_vel.sh b/tests/trajectory-planner/circular-arcs/util/save_vel.sh
index 16d43718ee5..48f10e31b6b 100755
--- a/tests/trajectory-planner/circular-arcs/util/save_vel.sh
+++ b/tests/trajectory-planner/circular-arcs/util/save_vel.sh
@@ -1,7 +1,7 @@
 #!/bin/bash
 set -o nounset                              # Treat unset variables as an error
 
-if [ -a $1 ] 
+if [ -a "$1" ] 
 then
-    awk '/tc state/ {print $5,$8,$11}' $1 > vel_data.log
+    awk '/tc state/ {print $5,$8,$11}' "$1" > vel_data.log
 fi