glsl-vs-functions: 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/glsl-vs-functions - from package: piglit

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

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