qucsattenuator: 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/qucsattenuator - from package: qucs

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

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