This script installs WordPress inside a sub directory

wp-install-core-sub-dir.sh

#!/bin/bash

# Installation:

## Download the script to your home directory
# Make sure it has execute permissions (`chmod +x wp-install-core-sub-dir.sh`).
# Install the script in one of the folders in your PATH. (`mv wp-install-core-sub-dir.sh /usr/local/bin/wp-install-core-sub-dir`)

#Usage:

# $ mkdir mysite
# $ cd mysite
# $ wp-install-core-sub-dir {sub-directory} {db_name} {db_user} {db_pass} {site_url} "{site_title}" {admin_user} {admin_pass} {admin_email}

CORE_DIR=${1-'wp'}
DB_NAME=${2-'wordpress'}
DB_USER=${3-'root'}
DB_PASS=${4-'password'}

SITE_URL=${5-'https://wordpress.test'}
SITE_TITLE=${6-'WordPress Site in a Subdirectory'}
SITE_USER=${7-'admin'}
SITE_PASS=${8-'password'}
SITE_EMAIL=${9-'your@email.com'}

# create the dir for the core files
mkdir $CORE_DIR
cd $CORE_DIR

# download WordPress files
wp core download

# create the wp-config.php file
wp config create --dbname=$DB_NAME --dbuser=$DB_USER --dbpass=$DB_PASS

# create the database
wp db create

# install WordPress (less than 5 mins)
wp core install --url=$SITE_URL --title="$SITE_TITLE" --admin_user=$SITE_USER --admin_password=$SITE_PASS --admin_email=$SITE_EMAIL

# Copy (not move) index.php file to root
cd ../
cp "$CORE_DIR/index.php" ./index.php

# Edit index.php to point to correct path of wp-blog-header.php
perl -p -i -e "s/\/wp-blog-header/\/$CORE_DIR\/wp-blog-header/g" index.php

# Update the siteurl in the database with sub directory path
cd $CORE_DIR
wp option update siteurl $(wp option get siteurl)/$CORE_DIR

# Uncomment the below line if you want the config in root
#cp "$CORE_DIR/wp-config.php" ./wp-config.php

echo 'Install finished!'

Iain, thank you! few corrections that were needed to make this script work on my cPanel setup.

1. line 47: sed -i '' ... drop the ''

2. line 50: wp option update siteurl $(wp option get siteurl)/$CORE_DIR you need to add the path here too: wp option update siteurl $(wp option get siteurl --path=$CORE_DIR)/$CORE_DIR --path=$CORE_DIR

3. in order to prep empty database and user in a cPanel environment, use UAPI command like this:

# cPanel API: This creates DB and USER in such a way that cPanel can track this new db and user
uapi --output=json Mysql create_database name="$DB_NAME"
uapi --output=json Mysql create_user name="$DB_USER" password="$DB_PASS"
uapi Mysql set_privileges_on_database user="$DB_USER" database="$DB_NAME" privileges=ALL%20PRIVILEGES