# write $source to $file with file-locking
sub append_file_source {
    local($file,$source) = @_;
    local($e);
    local($LOCK_EX) = 2;
    local($LOCK_NB) = 4;
    local($LOCK_UN) = 8;

    open(F, ">> $file") || die "$file: $!\n";
    print "Lock $file.\n" if $verbose > 1;
    if (!flock(F, $LOCK_EX | $LOCK_NB)) {
        return;
    }
    print F join("\n", $source) . "\n";
    close F;
    flock(F, $LOCK_UN);
}


# write $username, $fullname, etc. to $file with file-locking
sub append_file_account {
    local($file, $username, $fullname, $phone, $maddress, $group, $contact) = @_;
    local($e);
    local($LOCK_EX) = 2;
    local($LOCK_NB) = 4;
    local($LOCK_UN) = 8;

    open(F, ">> $file") || die "$file: $!\n";
    print "Lock $file.\n" if $verbose > 1;
    if (!flock(F, $LOCK_EX | $LOCK_NB)) {
        return;
    }
    print F join(" - ", $username, $fullname, $phone, $maddress, $group, $contact) . "\n";
    close F;
    flock(F, $LOCK_UN);
}