memcexist: 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 Debian possible default full paths are:

/usr/bin/memcexist - from package: libmemcached-tools

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

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