unicornscan: 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:

/usr/bin/unicornscan - from package: unicornscan

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

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