gdl: 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/gdl - from package: gdl

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

On Debian possible default full paths are:

/usr/bin/gdl - from package: gnudatalanguage

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

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