spent: 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/spent - from package: opensp

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

On Debian possible default full paths are:

/usr/bin/spent - from package: sp

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

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