whichman: 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/whichman - from package: whichman

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

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