postprocessing_benchmark: 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/postprocessing_benchmark - from package: LibRaw-samples

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

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