wvunpack: 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/wvunpack - from package: wavpack

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

On Debian possible default full paths are:

/usr/bin/wvunpack - from package: wavpack

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

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