clac: 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/clac - from package: clac

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

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