pwhois: 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/pwhois - from package: pwhois

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

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