gfal-ls: 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-ls - from package: gfal2-util

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

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