delete-backup.sh

#!/bin/sh
# vim:ts=4 sw=4 sts=4 et:

BACKUP_DIR=/path/to/dir/which/has/yyyymmdd/dirs/under/the/directory

ask() {
    default=$1
    msg=$2

    echo -n "$msg" >&2
    read answer || return 1
    [ -n "$default" -a -z "$answer" ] && answer=$default
    echo -n "$answer"
    return 0
}

die() {
    echo "$@"
    exit 1
}


cd "$BACKUP_DIR" || die "error: can't chdir to '$BACKUP_DIR'."


echo
echo "[info] Ctrl-C to exit any prompt..."
echo

nohup=false
if ask y 'nohup? [Y/n]: ' | egrep -q '^[yY]'; then
    nohup=true
fi


# Loop until existing & correct date directory is given.
# e.g.)
# * yyyy/mm/dd
# * yyyy/mm
# * yyyy
while :; do
    # List yyyy/mm/dd dir.
    ls -d [0-9][0-9][0-9][0-9]/[0-9][0-9]/[0-9][0-9]
    ymd_dir=`ask '' 'which date?: '`
    # Handle EOF.
    [ $# -ne 0 ] && exit $#
    [ -d "$ymd_dir" ] || continue
    (echo "$ymd_dir" | egrep -q '^[0-9]{4}/[0-9]{2}/[0-9]{2}$') && break
    (echo "$ymd_dir" | egrep -q '^[0-9]{4}/[0-9]{2}/?$') && break
    (echo "$ymd_dir" | egrep -q '^[0-9]{4}/?$') && break
done

emptydir=`mktemp -d`
# A faster way to delete millions of files in a directory
# http://linuxnote.net/jianingy/en/linux/a-fast-way-to-remove-huge-number-of-files.html
delcmd="rsync -a --delete '$emptydir/' '$ymd_dir/'; rmdir '$emptydir'; rmdir -p '$ymd_dir' 2>/dev/null"
if $nohup; then
    # * Change process group ID by perl.
    # * Run with nohup(1) not to die with login shell.
    perl -e "setpgrp; exec @ARGV" -- nohup sh -c "$delcmd" >/dev/null 2>&1 &
    # NOTE: If you want to run 'watch' command in this script,
    # you need to call setpgrp(2) for above 'nohup' command.
    # Because SIGINT will be sent to process group
    # including 'nohup' process.
    # ('nohup' command doesn't ignore SIGINT, only SIGHUP)
    #trap 'echo "trapped SIGINT: $?"' 2
    watch -n1 'uptime; echo; ps awuxx | egrep -w [r]sync | fgrep -v watch; echo; df -h
| egrep "Filesystem|/mnt/"; echo; ls -Cd '"$ymd_dir"'/*'
    # Not reached here because of Ctrl-C(SIGINT).
else
    sh -c "$delcmd"
fi