r300-readcache: 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/lib64/piglit/bin/r300-readcache - from package: piglit

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

Error in other languages:
r300-readcache: bevel nie gevind nie
r300-readcache: comandă negăsită
r300-readcache: comando não encontrado
r300-readcache: commande introuvable
r300-readcache: command not found
r300-readcache: käsku ei ole
r300-readcache: không tìm thấy lệnh
r300-readcache: komanda nerasta
r300-readcache: Kommando nicht gefunden.
r300-readcache: kommandot finns inte
r300-readcache: komut yok
r300-readcache: nie znaleziono polecenia
r300-readcache: níor aimsíodh an t-ordú
r300-readcache: no se encontró la orden
r300-readcache: no s'ha trobat l'ordre
r300-readcache: opdracht niet gevonden
r300-readcache: parancs nem található
r300-readcache: perintah tidak ditemukan
r300-readcache: príkaz nenájdený
r300-readcache: příkaz nenalezen
r300-readcache: команда не найдена
r300-readcache: командата не е открита
r300-readcache: 命令找不到
r300-readcache: コマンドが見つかりません