[#1574] make all shell scripts POSIX compliant

* solve all shellcheck warnings
* shebang in all scripts
* set -eu everywhere
* make scripts callable from everywhere
* quote variables to prevent globbing and word splitting
* add missing copyrights
* remove unused variables
* use $() instead of backticks ``
... and so on

src/share/database/scripts/mysql/upgrade_8.1_to_8.2.sh.in

@@ -1,78 +1,88 @@
 #!/bin/sh
 
-prefix=@prefix@
+# Copyright (C) 2019-2020 Internet Systems Consortium, Inc. ("ISC")
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# shellcheck disable=SC1091
+# SC1091: Not following: ... was not specified as input (see shellcheck -x).
+
+# shellcheck disable=SC2039
+# SC2039: In POSIX sh, 'local' is undefined.
+
+# Exit with error if commands exit with non-zero and if undefined variables are
+# used.
+set -eu
+
+# shellcheck disable=SC2034
+# SC2034: ... appears unused. Verify use (or export if used externally).
+prefix="@prefix@"
+
 # Include utilities. Use installed version if available and
 # use build version if it isn't.
 if [ -e @datarootdir@/@PACKAGE_NAME@/scripts/admin-utils.sh ]; then
-    . @datarootdir@/@PACKAGE_NAME@/scripts/admin-utils.sh
+    . "@datarootdir@/@PACKAGE_NAME@/scripts/admin-utils.sh"
 else
-    . @abs_top_builddir@/src/bin/admin/admin-utils.sh
+    . "@abs_top_builddir@/src/bin/admin/admin-utils.sh"
 fi
 
-VERSION=`mysql_version "$@"`
-
-# We need to set global RESULT when we exit. This is checked by callers.
-bail() {
-    RESULT=$1
-    exit $1
-}
+VERSION=$(mysql_version "$@")
 
 if [ "$VERSION" != "8.1" ]; then
-    printf "This script upgrades 8.1 to 8.2. Reported version is $VERSION. Skipping upgrade.\n"
-    bail 0
+    printf 'This script upgrades 8.1 to 8.2. '
+    printf 'Reported version is %s. Skipping upgrade.\n' "${VERSION}"
+    exit 0
 fi
 
 # Get the schema name from database argument. We need this to
 # query information_schema for the right database.
-for arg in $@
+for arg in "${@}"
 do
-    cnt=`echo $arg | grep -c "^\-\-"`
-    if [ $cnt -eq 0 ]
+    if ! grep -Eq '^\-\-' <<<"${arg}"
     then
         schema="$arg"
-        break;
+        break
     fi
 done
 
 # Make sure we can id the schema
-if [ -z $schema ]
+if [ -z "$schema" ]
 then
-    printf "Could not find database schema name in cmd line args: $@\n"
-    bail 255
+    printf "Could not find database schema name in cmd line args: %s\n" "${*}"
+    exit 255
 fi
 
-# Save the command line args, as we use these later change_column function. 
-cmdargs="$@"
+# Save the command line args, as we use these later change_column function.
+cmdargs=("${@}")
 
 # Function to rename a column in a table.
 change_column() {
-    local schema="$1"
-    local table="$2"
-    local ocolumn="$3"
-    local ncolumn="$4"
+    local schema="${1-}"
+    local table="${2-}"
+    local ocolumn="${3-}"
+    local ncolumn="${4-}"
 
     # First let's find out if the column name in the table actually needs updating.
     sql="select count(column_name) from information_schema.columns where table_schema='$schema' and table_name = '$table' and column_name = '$ocolumn'"
-
-    count=`mysql -N -B $cmdargs -e "$sql"`
-    if [ $? -ne 0 ]
+    if ! count=$(mysql -N -B "${cmdargs[@]}" -e "$sql")
     then
-        printf "change_column: schema query failed [$sql]\n"
-        bail 255;
+        printf 'change_column: schema query failed [%s]\n' "${sql}"
+        exit 255
     fi
 
-    # If we found a match record, the column needs to be renamed 
+    # If we found a match record, the column needs to be renamed
     if [ "$count" -eq 1 ]
     then
         sql="ALTER TABLE $table CHANGE COLUMN $ocolumn $ncolumn"
-        mysql -N -B $cmdargs -e "$sql"
-        if [ $? -ne 0 ]
+        if ! mysql -N -B "${cmdargs[@]}" -e "$sql"
         then
-            printf "change_column: alter query failed: [$sql]\n"
-            bail 255;
+            printf 'change_column: alter query failed [%s]\n' "${sql}"
+            exit 255
         fi
     else
-        printf "$table column is already correct\n"
+        printf '%s column is already correct\n' "${table}"
     fi
 }
 
@@ -485,15 +495,7 @@ SET version = '8', minor = '2';
 
 EOF
 
-RESULT=$?
-if [ $RESULT -ne 0 ]
-then
-    exit $RESULT
-fi
-
 # We need to rename the columns in the option def tables because "array" is
 # a MySQL keyword as of 8.0.17
-change_column $schema dhcp4_option_def array "is_array TINYINT(1) NOT NULL"
-change_column $schema dhcp6_option_def array "is_array TINYINT(1) NOT NULL"
-
-bail 0
+change_column "${schema}" dhcp4_option_def array "is_array TINYINT(1) NOT NULL"
+change_column "${schema}" dhcp6_option_def array "is_array TINYINT(1) NOT NULL"