proxycheck: 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/proxycheck - from package: proxycheck

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

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