Many-Domain script

#!/bin/sh
# This script converts the vpopmail db traditionally used by QMT with domain
# tables (domain_tld) to the vpopmail table containing many domains (md).
# In addition to this vpopmail db conversion appropriate replacement packages
# must be installed to interact with the converted vpopmail db, specifically,
# CentOS 7/8 pkgs designated with 'md'. The conversion was necessary not only
# for Dovecot's dsync utility to utilize commands like `doveadm user '*'` which
# fails with Dovecot's vpopmail driver but because Dovecot is dropping support
# for the vpopmail driver.

passwd=
read -s -p "Enter your MySQL DB management password: " passwd
echo ""
if [ "$passwd" == "" ];
then
   echo "You must enter the MySQL DB management password"
   exit 0
fi

MYSQLPW=$passwd
credfile=~/sql.cnf
echo -e "[client]\nuser=root\npassword='$MYSQLPW'\nhost=localhost" > $credfile

mysql --defaults-extra-file=$credfile -e "use vpopmail"
[ "$?" != "0" ] && echo "Password error, exiting..." && exit 1

DB=vpopmail

mysql --defaults-extra-file=$credfile -D $DB -e "CREATE TABLE vpopmail \
(pw_name char(32) NOT NULL, \
pw_domain char(96) NOT NULL, \
pw_passwd char(40) DEFAULT NULL, \
pw_uid int(11) DEFAULT NULL, \
pw_gid int(11) DEFAULT NULL, \
pw_gecos char(48) DEFAULT NULL, \
pw_dir char(160) DEFAULT NULL, \
pw_shell char(20) DEFAULT NULL,\
pw_clear_passwd char(16) DEFAULT NULL, \
PRIMARY KEY (pw_name,pw_domain)) ENGINE=InnoDB DEFAULT CHARSET=latin1"
[ "$?" != "0" ] && echo "Error creating vpopmail table" && exit 1
for i in `echo "show tables" | mysql --defaults-extra-file=$credfile -D $DB|grep -v Tables_in_`;
do
       if ! [ $i = dir_control ] && ! [ $i = lastauth ] && ! [ $i = vlog ] && ! [ $i = valias ] && ! [ $i = vpopmail ]; then
               # MySQL does not allow table names with a dot (.) so vpopmail replaces the dot (.) with an underscore (_) for
               # domain table names, example: table whitehorsetc.com becomes whitehorsetc_com. Vpopmail utilities will not allow
               # one to create a domain name with an underscore even though RFC allows it. So, we can safely replace all domain
               # table name underscores (_) with periods or dots (.) (below, 'domain_name') in our conversion for entry into the
               # new vpopmail many domains table.
               domain_name=`echo $i | sed -e 's/\(.*\)_/\1./' -e 's/_/-/g'`
               echo $domain_name;
               mysql --defaults-extra-file=$credfile -D $DB -B --skip-column-names -e \
               "INSERT INTO vpopmail SELECT pw_name, '$domain_name', pw_passwd, pw_uid, pw_gid, pw_gecos, pw_dir, pw_shell, pw_clear_passwd \
               FROM $i"
       fi
done