gnuclient: 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/gnuclient - from package: xemacs

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

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