webcheck: 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/webcheck - from package: webcheck

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

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