glx-shader-sharing: 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/glx-shader-sharing - from package: piglit

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

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