xrdgsiproxy: 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/xrdgsiproxy - from package: xrootd-client

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

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