psxyz: 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/psxyz - 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/psxyz - from package: GMT

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

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