cavern: 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/cavern - from package: survex

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

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