whowatch: 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 Debian possible default full paths are:

/usr/bin/whowatch - from package: whowatch

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

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