gmtget: 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/gmtget - from package: GMT

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

On Debian possible default full paths are:

/usr/lib/gmt/bin/gmtget - from package: GMT

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

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