ng4ex: 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/ng4ex - from package: ncl-examples

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

On Debian possible default full paths are:

/usr/bin/ng4ex - from package: libncarg-bin

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

Error in other languages:
ng4ex: bevel nie gevind nie
ng4ex: comandă negăsită
ng4ex: comando não encontrado
ng4ex: commande introuvable
ng4ex: command not found
ng4ex: käsku ei ole
ng4ex: không tìm thấy lệnh
ng4ex: komanda nerasta
ng4ex: Kommando nicht gefunden.
ng4ex: kommandot finns inte
ng4ex: komut yok
ng4ex: nie znaleziono polecenia
ng4ex: níor aimsíodh an t-ordú
ng4ex: no se encontró la orden
ng4ex: no s'ha trobat l'ordre
ng4ex: opdracht niet gevonden
ng4ex: parancs nem található
ng4ex: perintah tidak ditemukan
ng4ex: príkaz nenájdený
ng4ex: příkaz nenalezen
ng4ex: команда не найдена
ng4ex: командата не е открита
ng4ex: 命令找不到
ng4ex: コマンドが見つかりません