jack-osc: 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/jack-osc - from package: jack-tools

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

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