suspend-mail-delivery

#!/bin/bash
# Use unofficial bash strict mode http://redsymbol.net/articles/unofficial-bash-strict-mode/
set -euo pipefail
IFS=$'\n\t'

# Credit to http://stackoverflow.com/a/246128
DIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )

args=${1:-}
prog=${0:-}
banner_written="false"

etcmail="/etc/mail"
vut="$etcmail/virtusertable"
suspension_letter="/var/local/obscure/ops/suspend-mail.txt"
hosts="obscure.org tiamat.obscure.org"

write_banner() {
    if ! "$banner_written"; then 
        echo "# suspend-mail-delivery run at $(date --rfc-3339=seconds)" >> /etc/mail/virtusertable
        banner_written="true"
    fi
}

tick() {
    echo -n "."
}

suspend_user() {
    user=${1:-}
    if ! id "$user" > /dev/null; then
        return 2
    else
        mbox="/var/spool/mail/$user"
        zipfile="/home/$user/inbox-old.zip"
        lockfile="$mbox.lock"
        echo -n "suspending $user "
        (
            trap "rm -f $lockfile" EXIT
            flock -e -w 60 200
            # ... commands executed under lock ...
            tick
            zip -9 -q < "$mbox" > "$zipfile"
            tick
            cat /dev/null > "$mbox"
        ) 200>"$lockfile"
        rm -f "$lockfile"
        chown "$user":"$user" "$zipfile"
        chmod 0600 "$zipfile"
        tick
        /usr/sbin/sendmail -t "$user" < "$suspension_letter"
        sleep 10 # wait for new mail to be delivered, normally quick
        tick
        write_banner
        for host in $hosts; do
            echo "$user@$host error:5.2.1:521 \"Mail delivery for this user has been disabled by the administrator.\"" >> /etc/mail/virtusertable
        done
        cd "$etcmail"
        make
        cd - > /dev/null 2>&1
        tick
        echo " done"
    fi
}
if [[ $(id -u) -ne 0 ]]; then
    echo "$prog: Must be run as root, aborting."
    exit 1
elif [[ -z "$args" ]]; then
    echo "$prog: syntax: suspend-mail-delivery <username|--inactive>"
    exit 1
elif [[ "$args" == "--inactive" ]]; then 
    # Suspend all inactive users
    . "$DIR/find-active-email-users"
    find_inactive_mail_users_to_suspend | while read user; do 
        suspend_user "$user" || echo "Could not suspend user $user"
    done
else
    # Suspend one user
    suspend_user "$args"
fi