diff --git a/bin/tcp-connection-state-counter b/bin/tcp-connection-state-counter
index 6629e8fb..cbebc013 100755
--- a/bin/tcp-connection-state-counter
+++ b/bin/tcp-connection-state-counter
@@ -35,7 +35,7 @@ EOF
 }
 
 progVersion() {
-  echo "$PROG $PROG_VERSION"
+  printf '%s\n' "$PROG $PROG_VERSION"
   exit
 }
 
@@ -58,6 +58,7 @@ done
 # On MacOS, netstat need to using -p tcp to get only tcp output.
 uname | grep Darwin -q && option_for_mac="-ptcp"
 
+# shellcheck disable=SC2086
 netstat -tna ${option_for_mac:-} | awk 'NR > 2 {
     ++s[$NF]
 }
diff --git a/lib/console-text-color-themes.sh b/lib/console-text-color-themes.sh
index dcff9380..63de93ff 100755
--- a/lib/console-text-color-themes.sh
+++ b/lib/console-text-color-themes.sh
@@ -37,55 +37,64 @@ colorEcho() {
   local combination="$1"
   shift 1
 
-  [ -t 1 ] && echo "${_ctct_ec}[${combination}m$*$_ctct_eend" || echo "$*"
+  if [ -t 1 ]; then
+    echo "${_ctct_ec}[${combination}m$*$_ctct_eend"
+  else
+    echo "$*"
+  fi
 }
 
 colorEchoWithoutNewLine() {
   local combination="$1"
   shift 1
 
-  [ -t 1 ] && echo -n "${_ctct_ec}[${combination}m$*$_ctct_eend" || echo -n "$*"
+  if [ -t 1 ]; then
+    echo -n "${_ctct_ec}[${combination}m$*$_ctct_eend"
+  else
+    echo -n "$*"
+  fi
 }
 
 # if not directly run this script(use as lib), just export 2 helper functions,
 # and do NOT print anything.
-[ "$_ctct_is_direct_run" == "true" ] && {
+[ "$_ctct_is_direct_run" == true ] && {
   for style in 0 1 2 3 4 5 6 7; do
     for fg in 30 31 32 33 34 35 36 37; do
       for bg in 40 41 42 43 44 45 46 47; do
         combination="${style};${fg};${bg}"
         colorEchoWithoutNewLine "$combination" "$combination"
-        echo -n " "
+        printf ' '
       done
       echo
     done
     echo
   done
 
-  echo "Code sample to print color text:"
+  echo 'Code sample to print color text:'
 
   echo -n '    echo -e "\033['
-  colorEchoWithoutNewLine "3;35;40" "1;36;41"
-  echo -n "m"
-  colorEchoWithoutNewLine "0;32;40" "Sample Text"
-  echo "\033[0m\""
+  colorEchoWithoutNewLine '3;35;40' '1;36;41'
+  echo -n m
+  colorEchoWithoutNewLine '0;32;40' 'Sample Text'
+  echo '\033[0m"'
 
   echo -n "    echo \$'\033["
-  colorEchoWithoutNewLine "3;35;40" "1;36;41"
+  colorEchoWithoutNewLine '3;35;40' '1;36;41'
   echo -n "m'\""
-  colorEchoWithoutNewLine "0;32;40" "Sample Text"
+  colorEchoWithoutNewLine '0;32;40' 'Sample Text'
   echo "\"$'\033[0m'"
   echo "      # NOTE: $'foo' is the escape sequence syntax of bash, safer escape"
 
-  echo "Output of above code:"
-  echo "    ${_ctct_ec}[1;36;41mSample Text${_ctct_eend}"
+  echo 'Output of above code:'
+  echo -n '    '
+  colorEcho '1;36;41' 'Sample Text'
   echo
-  echo "If you are going crazy to write text in escapes string like me,"
-  echo "you can use colorEcho and colorEchoWithoutNewLine function in this script."
+  echo 'If you are going crazy to write text in escapes string like me,'
+  echo 'you can use colorEcho and colorEchoWithoutNewLine function in this script.'
   echo
-  echo "Code sample to print color text:"
+  echo 'Code sample to print color text:'
   echo '    colorEcho "1;36;41" "Sample Text"'
-  echo "Output of above code:"
-  echo -n "    "
-  colorEcho "1;36;41" "Sample Text"
+  echo 'Output of above code:'
+  echo -n '    '
+  colorEcho '1;36;41' 'Sample Text'
 }