test-plugs: 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/test-plugs - from package: libiec61883-utils

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

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