user_list: 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/user_list - from package: libstatgrab-examples

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

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