Migrate a database from one MySQL host to another

db-migrator.sh

#! /bin/bash
# @author Ash Davies <a.davies@mixd.co.uk>

FROM=$1
TO=$2
FILENAME=wp-config.php
BACKUP_FIRST=yes
TMP=$(mktemp)

# Terminate on any errors
set -e

echo "[!] WARNING"
echo "[!] Please ensure you have already created the new database on your target host before continuing"
echo "[!] This script does not accommodate creation of new databases. It will simply export/import from old to new"
echo
echo

asksure() {
    echo -n "Are you sure you want to continue (Y/N)? "
    echo

    while read -r -n 1 -s answer; do
        if [[ $answer = [YyNn] ]]; then
            [[ $answer = [Yy] ]] && retval=0
            [[ $answer = [Nn] ]] && retval=1
            break
        fi
    done
    echo

    return $retval
}

searchreplace() {
    str=$(sed --version 2> /dev/null | head -n 1);
    sub="GNU Sed";
    #bin=$(command -v 'sed' || which 'sed' || type -p 'sed');
    pattern="s/$1/$2/g"

    echo "Performing search and replace pattern '$pattern' on '$3'"

    #if [[ "$str" == *"$sub"* ]]; then
    #    $bin -i $pattern $3
    #else
    #    $bin -i '' $pattern $3
    #fi
    sed -i --follow-symlinks $pattern $3

    echo
}

backup_db() {
    echo "Creating database backup from old host"
    echo "[i] $(wp db export $TMP)"
    echo
}

push_db() {
    echo "Importing database backup to new host"
    echo "[i] $(wp db import $TMP)"
    echo
}

cleanup() {
    echo "Deleting previous backup"
    rm $TMP
    echo

    echo "Disabling maintenance mode"
    rm $(pwd -P)/wordpress/.maintenance
    echo
}

scandir() {
    echo "Scanning $(pwd -P) for files that match '$FILENAME'"

    ls $(pwd -P) | grep -w "$FILENAME" &> /dev/null;

    if [ "$?" = "0" ];
        then
            FILE="$(pwd -P)/$FILENAME"
            echo "[i] Found $FILE"
            echo

            # if grep -q "DB_HOST.*[\"']\K$FROM(?=[\"'])" $FILE;
            if grep -q $FROM $FILE;
                then
                    echo "Found reference to old db host '$FROM'"
                    echo

                    echo "Creating wp-config.php backup"
                    echo "[i] $(cp -nfv $FILE{,.old.php})"
                    echo

                    echo "Enabling maintenance mode"
                    touch $(pwd -P)/wordpress/.maintenance
                    echo "<?php \$upgrading = time(); ?>" > $(pwd -P)/wordpress/.maintenance

                    backup_db
                    searchreplace $FROM $TO $FILE
                    push_db

                    cleanup
            else
                echo "Error: Cannot find reference to old db host"
                exit 1
            fi
    else
        echo "Can't find any files"
        exit 1
    fi
}

if [ -z "$2" ]
    then
        echo "Error: Please specify the database hostnames as arguments wrapped in quotes"
        exit 1
fi

echo "I'm going to look for all references of '$FROM' and replace it with '$TO'."

if asksure;
    then
        scandir;
else
    exit 1
fi