tgks0a: 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/tgks0a - from package: ncl

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

On Debian possible default full paths are:

/usr/bin/tgks0a - from package: ncl-ncarg

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

Error in other languages:
tgks0a: bevel nie gevind nie
tgks0a: comandă negăsită
tgks0a: comando não encontrado
tgks0a: commande introuvable
tgks0a: command not found
tgks0a: käsku ei ole
tgks0a: không tìm thấy lệnh
tgks0a: komanda nerasta
tgks0a: Kommando nicht gefunden.
tgks0a: kommandot finns inte
tgks0a: komut yok
tgks0a: nie znaleziono polecenia
tgks0a: níor aimsíodh an t-ordú
tgks0a: no se encontró la orden
tgks0a: no s'ha trobat l'ordre
tgks0a: opdracht niet gevonden
tgks0a: parancs nem található
tgks0a: perintah tidak ditemukan
tgks0a: príkaz nenájdený
tgks0a: příkaz nenalezen
tgks0a: команда не найдена
tgks0a: командата не е открита
tgks0a: 命令找不到
tgks0a: コマンドが見つかりません