Finds Wordpress installations with outdated cores and/or plugins. If it throws php warnings (wp-cli does so), just redirect do `wp-update-check.sh 2>/dev/null`.

wp-upgrade-check.sh

#!/usr/bin/env bash
 
#
# Script will find all wordpress installs and check if they're out of date
#
 
# Using wp-cli - http://wp-cli.org/
 
# Paths to search for wordpresses. Separated by space.
PATHS="/var/www /data/www"
# Paths to ignore (should not be checked). Separated by space.
IGNOREPATHS="/var/www/dev-site /var/www/other-site/backup"
 
WPCLI=/usr/local/bin/wp-cli
LATESTVERSION=$(curl -s http://api.wordpress.org/core/version-check/1.5/ | head -n 4 | tail -n 1)
WORDPRESSES=$(find $PATHS -type d -name "wp-includes" -print)
 
# Loop through results
for WPATH in $WORDPRESSES; do
    # Strip wp-includes from path
    WPATH=$(dirname $WPATH)
 
    # If folder is excluded, continue
    if [ "${IGNOREPATHS/$WPATH}" != "$IGNOREPATHS" ]; then
        continue;
    fi
 
    # Find out version
    VERSION=$($WPCLI --allow-root --path=$WPATH core version)
 
    # Compare versions. Do not care about downgrades.
    if [ "$LATESTVERSION" != "$VERSION" ]; then
        echo "$WPATH Versions differ. Update required $VERSION->$LATESTVERSION"
        echo "Fix: $WPCLI --allow-root --path=$WPATH core update"
        echo
    fi
 
    # List outdated plugins
    RESULT=$($WPCLI --allow-root --path=$WPATH plugin status | grep "^[[:space:]]U") && echo "$WPATH Some plugins are outdated:" && echo $RESULT && echo "Fix: $WPCLI --allow-root --path=$WPATH plugin update --all" && echo
 
done