whirlpoolsum: 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/whirlpoolsum - from package: libwhirlpool

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

On Debian possible default full paths are:

/usr/bin/whirlpoolsum - from package: libdigest-whirlpool-perl

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

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