ratop: 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/ratop - from package: argus-client

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

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