doctorj: command not found

Have You tried accessing the binary with the full path?

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/doctorj - from package: doctorj

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