longprim: command not found

Have You tried accessing the binary with the full path?

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/longprim - from package: piglit

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