tardiff: 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/tardiff - from package: tardiff

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

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