Locking for Bash scripts

lockfile.sh

#!/bin/bash
# See: http://www.kfirlavi.com/blog/2012/11/06/elegant-locking-of-bash-program/

readonly PROGNAME=$(basename "$0")
readonly LOCKFILE_DIR=/tmp
readonly LOCK_FD=200

lock() {
    local prefix=$1
    local fd=${2:-$LOCK_FD}
    local lock_file=$LOCKFILE_DIR/$prefix.lock

    # create lock file
    eval "exec $fd>$lock_file"

    # acquier the lock
    flock -n $fd \
        && return 0 \
        || return 1
}

eexit() {
    local error_str="$@"

    echo $error_str
    exit 1
}

main() {
    lock $PROGNAME \
        || eexit "Only one instance of $PROGNAME can run at one time."

    do_A
    do_B
}
main

Nice script!
But does it clear the lockfile once its stopped running?