kfile4: 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/kfile4 - from package: kdebase-runtime

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

On Debian possible default full paths are:

/usr/bin/kfile4 - from package: kde-runtime

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

Error in other languages:
kfile4: bevel nie gevind nie
kfile4: comandă negăsită
kfile4: comando não encontrado
kfile4: commande introuvable
kfile4: command not found
kfile4: käsku ei ole
kfile4: không tìm thấy lệnh
kfile4: komanda nerasta
kfile4: Kommando nicht gefunden.
kfile4: kommandot finns inte
kfile4: komut yok
kfile4: nie znaleziono polecenia
kfile4: níor aimsíodh an t-ordú
kfile4: no se encontró la orden
kfile4: no s'ha trobat l'ordre
kfile4: opdracht niet gevonden
kfile4: parancs nem található
kfile4: perintah tidak ditemukan
kfile4: príkaz nenájdený
kfile4: příkaz nenalezen
kfile4: команда не найдена
kfile4: командата не е открита
kfile4: 命令找不到
kfile4: コマンドが見つかりません