med: 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/med - from package: ncl

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

On Debian possible default full paths are:

/usr/bin/med - from package: ncl-ncarg

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

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