iwspy: 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 CentOS possible default full paths are:

/sbin/iwspy - from package: wireless-tools

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/sbin/iwspy - from package: wireless-tools

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

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