xzegrep: 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/xzegrep - from package: xz

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

On Debian possible default full paths are:

/usr/bin/xzegrep - from package: xz-utils

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

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