htcacheclean: 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/sbin/htcacheclean - from package: httpd

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

On Debian possible default full paths are:

/usr/bin/htcacheclean - from package: apache2-utils

You may install the required package with command apt-get install {package}

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