groupBy: 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/bin/groupBy - from package: BEDTools

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

On Debian possible default full paths are:

/usr/bin/groupBy - from package: filo

You may install the required package with command apt-get install {package}

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