qtoctave: 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/qtoctave - from package: qtoctave

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

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