nstclsh: 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/nstclsh - from package: aolserver4-daemon

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

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