grdvector: 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/grdvector - 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/grdvector - from package: GMT

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

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