btcompletedirgui.bittorrent: 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/btcompletedirgui.bittorrent - from package: bittorrent-gui

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

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