Fix bash syntax issues detected by Shellcheck

- Remove unused variable MYADMIN
- Correctly execute with $()
- Encapsulate variables in double quotes
- Use ] && [ instead of -a

debian/mariadb-server-10.1.postinst

@@ -45,7 +45,7 @@ case "$1" in
           mv "$savelink" "$targetdir"
         else
           # this should never even happen, but just in case...
-          mysql_tmp=`mktemp -d -t mysql-symlink-restore-XXXXXX`
+          mysql_tmp=$(mktemp -d -t mysql-symlink-restore-XXXXXX)
           echo "this is very strange!  see $mysql_tmp/README..." >&2
           mv "$targetdir" "$mysql_tmp"
           cat << EOF > "$mysql_tmp/README"
@@ -69,16 +69,16 @@ EOF
 
     # Ensure the existence and right permissions for the database and
     # log files.
-    if [ ! -d "$mysql_statedir" -a ! -L "$mysql_statedir" ]; then mkdir "$mysql_statedir"; fi
-    if [ ! -d "$mysql_datadir"  -a ! -L "$mysql_datadir" ]; then mkdir "$mysql_datadir" ; fi
-    if [ ! -d "$mysql_logdir"   -a ! -L "$mysql_logdir"  ]; then mkdir "$mysql_logdir"  ; fi
+    if [ ! -d "$mysql_statedir" ] && [ ! -L "$mysql_statedir" ]; then mkdir "$mysql_statedir"; fi
+    if [ ! -d "$mysql_datadir"  ] && [ ! -L "$mysql_datadir" ]; then mkdir "$mysql_datadir" ; fi
+    if [ ! -d "$mysql_logdir"   ] && [ ! -L "$mysql_logdir"  ]; then mkdir "$mysql_logdir"  ; fi
     # When creating an ext3 jounal on an already mounted filesystem like e.g.
     # /var/lib/mysql, you get a .journal file that is not modifyable by chown.
     # The mysql_statedir must not be writable by the mysql user under any
     # circumstances as it contains scripts that are executed by root.
     set +e
     chown -R 0:0 $mysql_statedir
-    find $mysql_datadir ! -uid $(id -u mysql) -print0 | xargs -0 -r chown mysql
+    find $mysql_datadir ! -uid "$(id -u mysql)" -print0 | xargs -0 -r chown mysql
     chown -R mysql:adm $mysql_logdir
     chmod 2750 $mysql_logdir
     set -e

debian/mariadb-server-10.1.preinst

@@ -18,7 +18,6 @@ if [ -n "$DEBIAN_SCRIPT_DEBUG" ]; then set -v -x; DEBIAN_SCRIPT_TRACE=1; fi
 ${DEBIAN_SCRIPT_TRACE:+ echo "#42#DEBUG# RUNNING $0 $*" 1>&2 }
 
 export PATH=$PATH:/sbin:/usr/sbin:/bin:/usr/bin
-MYADMIN="/usr/bin/mysqladmin --defaults-file=/etc/mysql/debian.cnf"
 mysql_datadir=/var/lib/mysql
 mysql_upgradedir=/var/lib/mysql-upgrade
 
@@ -36,12 +35,12 @@ do
   # The for loop leaves $flag as the query string if there are no results,
   # so the check below is needed to stop further processing when there are
   # no real results.
-  if [ $flag = "$mysql_datadir/debian-*.flag" ]
+  if [ "$flag" = "$mysql_datadir/debian-*.flag" ]
   then
     break
   fi
 
-  flag_version=`echo $flag | sed 's/.*debian-\([0-9\.]\+\).flag/\1/'`
+  flag_version=$(echo "$flag" | sed 's/.*debian-\([0-9\.]\+\).flag/\1/')
 
   # Initialize value if empty
   if [ -z "$found_version" ]
@@ -95,16 +94,16 @@ then
   echo "previous data directory will be renamed to $mysql_datadir-$found_version and" 1>&2
   echo "a new data directory will be initialized at $mysql_datadir." 1>&2
   echo "Please manually export/import your data (e.g. with mysqldump) if needed." 1>&2
-  mv -f $mysql_datadir $mysql_datadir-$found_version
+  mv -f "$mysql_datadir" "$mysql_datadir-$found_version"
   # Also move away the old debian.cnf file that included credentials that are
   # no longer valid
-  mv -f /etc/mysql/debian.cnf /etc/mysql/debian.cnf-$found_version
+  mv -f /etc/mysql/debian.cnf "/etc/mysql/debian.cnf-$found_version"
 fi
 
 # If we use NIS then errors should be tolerated. It's up to the
 # user to ensure that the mysql user is correctly setup.
 # Beware that there are two ypwhich one of them needs the 2>/dev/null!
-if test -n "`which ypwhich 2>/dev/null`"  &&  ypwhich >/dev/null 2>&1; then
+if test -n "$(which ypwhich 2>/dev/null)"  &&  ypwhich >/dev/null 2>&1; then
   set +e
 fi
 
@@ -144,7 +143,7 @@ set -e
 # if there's a symlink, let's store where it's pointing, because otherwise
 # it's going to be lost in some situations
 for dir in DATADIR LOGDIR; do
-    checkdir=`eval echo "$"$dir`
+    checkdir=$(eval echo "$"$dir)
     if [ -L "$checkdir" ]; then
 	mkdir -p "$mysql_upgradedir"
 	cp -dT "$checkdir" "$mysql_upgradedir/$dir.link"
@@ -152,7 +151,7 @@ for dir in DATADIR LOGDIR; do
 done
 
 # creating mysql home directory
-if [ ! -d $mysql_datadir -a ! -L $mysql_datadir ]; then
+if [ ! -d $mysql_datadir ] && [ ! -L $mysql_datadir ]; then
  	mkdir $mysql_datadir
 fi
 
@@ -171,7 +170,7 @@ fi
 # The "set +e" is necessary as e.g. a ".journal" of a ext3 partition is
 # not chgrp'able (#318435).
 set +e
-find $mysql_datadir ! -uid $(id -u mysql) -print0 | xargs -0 -r chown mysql
+find $mysql_datadir ! -uid "$(id -u mysql)" -print0 | xargs -0 -r chown mysql
 find $mysql_datadir -follow -not -group mysql -print0 2>/dev/null \
   | xargs -0 --no-run-if-empty chgrp mysql
 set -e