arb_sample_shading-api: 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/arb_sample_shading-api - from package: piglit

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

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