tauex: 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/tauex - from package: tau
/usr/lib/tau/x86_64/bin/tauex - from package: tau

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

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