htoclean: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/htoclean - from package: clean

You may install the required package with command yum install {package}

Error in other languages:
htoclean: bevel nie gevind nie
htoclean: comandă negăsită
htoclean: comando não encontrado
htoclean: commande introuvable
htoclean: command not found
htoclean: käsku ei ole
htoclean: không tìm thấy lệnh
htoclean: komanda nerasta
htoclean: Kommando nicht gefunden.
htoclean: kommandot finns inte
htoclean: komut yok
htoclean: nie znaleziono polecenia
htoclean: níor aimsíodh an t-ordú
htoclean: no se encontró la orden
htoclean: no s'ha trobat l'ordre
htoclean: opdracht niet gevonden
htoclean: parancs nem található
htoclean: perintah tidak ditemukan
htoclean: príkaz nenájdený
htoclean: příkaz nenalezen
htoclean: команда не найдена
htoclean: командата не е открита
htoclean: 命令找不到
htoclean: コマンドが見つかりません