clock: 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:

/sbin/clock - from package: util-linux-ng

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

On Debian possible default full paths are:

/usr/bin/clock - from package: xview-clients

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

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