gatttool: 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/gatttool - from package: bluez

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

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