diff --git a/.github/travis_build.sh b/.github/travis_build.sh
index 6b2fae8a..2e63a97f 100644
--- a/.github/travis_build.sh
+++ b/.github/travis_build.sh
@@ -5,16 +5,16 @@ set -e; set -o pipefail
 # Copyright (C) Markus Franz Xaver Johannes Oberhumer
 
 if [[ $TRAVIS_OS_NAME == osx ]]; then
-argv0=$0; argv0abs=$(greadlink -en -- "$0"); argv0dir=$(dirname "$argv0abs")
+    argv0=$0; argv0abs=$(greadlink -en -- "$0"); argv0dir=$(dirname "$argv0abs")
 else
-argv0=$0; argv0abs=$(readlink -en -- "$0"); argv0dir=$(dirname "$argv0abs")
+    argv0=$0; argv0abs=$(readlink -en -- "$0"); argv0dir=$(dirname "$argv0abs")
 fi
 source "$argv0dir/travis_init.sh" || exit 1
 
 # create dirs
 cd / || exit 1
 mkbuilddirs $upx_BUILDDIR $ucl_BUILDDIR $upx_testsuite_BUILDDIR $zlib_BUILDDIR
-cd / && cd $upx_SRCDIR || exit 1
+cd / && cd "$upx_SRCDIR" || exit 1
 
 echo
 print_settings
@@ -25,10 +25,10 @@ echo
 
 # check whitespace
 if [[ $TRAVIS_OS_NAME == linux ]]; then
-cd / && cd $upx_SRCDIR || exit 1
-echo "Checking source code for whitespace violations..."
-bash ./src/stub/scripts/check_whitespace.sh || exit 1
-echo "  Passed."
+    cd / && cd $upx_SRCDIR || exit 1
+    echo "Checking source code for whitespace violations..."
+    bash ./src/stub/scripts/check_whitespace.sh || exit 1
+    echo "  Passed."
 fi # linux
 
 set -x
@@ -45,7 +45,7 @@ if [[ $BM_X =~ (^|\+)rebuild-stubs($|\+) ]]; then
     else
         bin_upx=$(readlink -en -- "$upx_SRCDIR/../deps/bin-upx-20210104")
     fi
-    cd / && cd $upx_SRCDIR || exit 1
+    cd / && cd "$upx_SRCDIR" || exit 1
     extra_subdirs=()
     extra_subdirs+=( src/stub/src/arch/amd64 )
     extra_subdirs+=( src/stub/src/arch/arm/v4a )
@@ -92,7 +92,7 @@ fi
 # build UCL
 #
 
-cd / && cd $ucl_BUILDDIR || exit 1
+cd / && cd "$ucl_BUILDDIR" || exit 1
 # patch UCL
 sed 's/^#elif (ACC_ARCH_AMD64 || ACC_ARCH_IA64)$/& \&\& !defined(__ILP32__)/' $ucl_SRCDIR/acc/acc_chk.ch > a.tmp
 if cmp -s a.tmp $ucl_SRCDIR/acc/acc_chk.ch; then rm a.tmp; else mv a.tmp $ucl_SRCDIR/acc/acc_chk.ch; fi
@@ -115,7 +115,7 @@ fi
 #
 
 if [[ $BUILD_LOCAL_ZLIB == 1 ]]; then
-    cd / && cd $zlib_BUILDDIR || exit 1
+    cd / && cd "$zlib_BUILDDIR" || exit 1
     # build manually
     rm -f ./*.o libz.a
     $CC -O2 -c $zlib_SRCDIR/*.c
@@ -127,7 +127,7 @@ fi
 #
 
 export UPX_UCLDIR="$ucl_SRCDIR"
-cd / && cd $upx_BUILDDIR || exit 1
+cd / && cd "$upx_BUILDDIR" || exit 1
 make="make -f $upx_SRCDIR/src/Makefile"
 EXTRA_LDFLAGS="$EXTRA_LDFLAGS -L$ucl_BUILDDIR/src/.libs"
 if [[ $BUILD_LOCAL_ZLIB == 1 ]]; then
diff --git a/.github/travis_deploy.sh b/.github/travis_deploy.sh
index 62e59dda..f0b51fdc 100644
--- a/.github/travis_deploy.sh
+++ b/.github/travis_deploy.sh
@@ -5,9 +5,9 @@ set -e; set -o pipefail
 # Copyright (C) Markus Franz Xaver Johannes Oberhumer
 
 if [[ $TRAVIS_OS_NAME == osx ]]; then
-argv0=$0; argv0abs=$(greadlink -en -- "$0"); argv0dir=$(dirname "$argv0abs")
+    argv0=$0; argv0abs=$(greadlink -en -- "$0"); argv0dir=$(dirname "$argv0abs")
 else
-argv0=$0; argv0abs=$(readlink -en -- "$0"); argv0dir=$(dirname "$argv0abs")
+    argv0=$0; argv0abs=$(readlink -en -- "$0"); argv0dir=$(dirname "$argv0abs")
 fi
 source "$argv0dir/travis_init.sh" || exit 1
 
@@ -32,7 +32,7 @@ elif [[ -n $GITLAB_CI ]]; then
     branch=$CI_BUILD_REF_NAME
 else
     branch=$TRAVIS_BRANCH
-    if [[ "$TRAVIS_PULL_REQUEST" != "false" ]]; then exit 0; fi
+    if [[ $TRAVIS_PULL_REQUEST != "false" ]]; then exit 0; fi
 fi
 subdir=${subdir%%:*}; subdir=${subdir%%/*}; subdir=${subdir%%--*}
 case $branch in
@@ -45,9 +45,9 @@ case $branch in
 esac
 
 # get $rev, $branch and $git_user
-cd / && cd $upx_SRCDIR || exit 1
+cd / && cd "$upx_SRCDIR" || exit 1
 rev=$(git rev-parse --verify HEAD)
-if [[ "$branch" == gitlab* ]]; then
+if [[ $branch == gitlab* ]]; then
     if git fetch -v origin devel; then
         git branch -a -v
         rev=$(git merge-base origin/devel $rev || echo $rev)
@@ -74,7 +74,7 @@ unset timestamp date
 # // prepare directory $d
 # ************************************************************************/
 
-cd / && cd $upx_BUILDDIR || exit 1
+cd / && cd "$upx_BUILDDIR" || exit 1
 
 mkdir deploy || exit 1
 chmod 700 deploy
@@ -105,10 +105,10 @@ d=$d-$BM_C-$BM_B
 
 # remove redundant -m32/-m64/-x86/-x64 from directory name
 if [[ $d =~ ^((i386-darwin|i386-linux|i386-win32).*)(-m32|-x86)(-.+)?$ ]]; then
-   d="${BASH_REMATCH[1]}${BASH_REMATCH[4]}"
+    d="${BASH_REMATCH[1]}${BASH_REMATCH[4]}"
 fi
 if [[ $d =~ ^((amd64-darwin|amd64-linux|amd64-win64).*)(-m64|-x64)(-.+)?$ ]]; then
-   d="${BASH_REMATCH[1]}${BASH_REMATCH[4]}"
+    d="${BASH_REMATCH[1]}${BASH_REMATCH[4]}"
 fi
 
 if [[ -n $subdir ]]; then
diff --git a/.github/travis_init.sh b/.github/travis_init.sh
index 8f37fc6e..4347f9a7 100644
--- a/.github/travis_init.sh
+++ b/.github/travis_init.sh
@@ -140,7 +140,7 @@ if [[ -n $BM_CROSS ]]; then
         esac
     fi
 fi # BM_CROSS
-if [[ "$CC" == "false" ]]; then # generic
+if [[ $CC == "false" ]]; then # generic
 if [[ -z $BM_CROSS ]]; then
     if [[ $TRAVIS_OS_NAME == osx ]]; then
         case $BM_C in
@@ -199,7 +199,7 @@ mkbuilddirs() {
 }
 # search for an existing $toptop_builddir
 if [[ -z $toptop_builddir ]]; then
-    for d in . ..;  do
+    for d in . ..; do
         for subdir in "local" appveyor circle github gitlab travis .; do
             dd=$d/build/$subdir
             if [[ -d $dd ]]; then
diff --git a/.github/travis_testsuite_1.sh b/.github/travis_testsuite_1.sh
index e45f0345..f5dfbe80 100644
--- a/.github/travis_testsuite_1.sh
+++ b/.github/travis_testsuite_1.sh
@@ -9,9 +9,9 @@ set -e; set -o pipefail
 #
 
 if [[ $TRAVIS_OS_NAME == osx ]]; then
-argv0=$0; argv0abs=$(greadlink -en -- "$0"); argv0dir=$(dirname "$argv0abs")
+    argv0=$0; argv0abs=$(greadlink -en -- "$0"); argv0dir=$(dirname "$argv0abs")
 else
-argv0=$0; argv0abs=$(readlink -en -- "$0"); argv0dir=$(dirname "$argv0abs")
+    argv0=$0; argv0abs=$(readlink -en -- "$0"); argv0dir=$(dirname "$argv0abs")
 fi
 source "$argv0dir/travis_init.sh" || exit 1
 
@@ -27,7 +27,7 @@ fi
 # create dirs
 cd / || exit 1
 mkbuilddirs $upx_testsuite_BUILDDIR
-cd / && cd $upx_testsuite_BUILDDIR || exit 1
+cd / && cd "$upx_testsuite_BUILDDIR" || exit 1
 if [[ ! -d $upx_testsuite_SRCDIR/files/packed ]]; then exit 1; fi
 
 # /***********************************************************************
@@ -43,7 +43,7 @@ testsuite_split_f() {
     fb=$(basename "$1")
     fsubdir=$(basename "$fd")
     # sanity checks
-    if [[ ! -f "$1" || -z "$fsubdir" || -z "$fb" ]]; then
+    if [[ ! -f $1 || -z $fsubdir || -z $fb ]]; then
         fd= fb= fsubdir=
     fi
 }
@@ -111,7 +111,7 @@ testsuite_run_compress() {
 # ************************************************************************/
 
 recreate_expected_sha256sums() {
-    local o="$1"
+    local o=$1
     local files f d
     echo "########## begin .sha256sums.recreate" > "$o"
     files=*/.sha256sums.current
@@ -163,7 +163,7 @@ if [[ $BM_T =~ (^|\+)valgrind($|\+) ]]; then
 fi
 
 if [[ $BM_B =~ (^|\+)coverage($|\+) ]]; then
-    (cd / && cd $upx_BUILDDIR && lcov -d . --zerocounters)
+    (cd / && cd "$upx_BUILDDIR" && lcov -d . --zerocounters)
 fi
 
 export UPX="--prefer-ucl --no-color --no-progress"
@@ -194,7 +194,6 @@ for f in $upx_testsuite_SRCDIR/files/packed/*/upx-3.9[15]*; do
 done
 testsuite_check_sha $testdir
 
-
 # run one pack+unpack step to canonicalize the files
 testdir=t020_canonicalized
 mkdir $testdir; v=expected_sha256sums__$testdir; echo -n "${!v}" >$testdir/.sha256sums.expected
@@ -248,7 +247,7 @@ time testsuite_run_compress --all-methods --no-lzma -5 --no-filter
 # // summary
 # ************************************************************************/
 
-# recreate checkums from current version for an easy update in case of changes
+# recreate checksums from current version for an easy update in case of changes
 recreate_expected_sha256sums .sha256sums.recreate
 
 testsuite_header "UPX testsuite summary"
@@ -258,10 +257,10 @@ if ! $upx_run --version; then
 fi
 echo
 echo "upx_exe='$upx_exe'"
-if [[ "$upx_run" != "$upx_exe" ]]; then
+if [[ $upx_run != "$upx_exe" ]]; then
     echo "upx_run='$upx_run'"
 fi
-if [[ -f "$upx_exe" ]]; then
+if [[ -f $upx_exe ]]; then
     ls -l "$upx_exe"
     file "$upx_exe" || true
 fi