sleepenh: 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/sleepenh - from package: sleepenh

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

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