grdedit: 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/grdedit - 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/grdedit - from package: GMT

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

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