process_stats: 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/process_stats - from package: libstatgrab-examples

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

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