gfal_version: 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/gfal_version - from package: gfal

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

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