kshell4: 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/kshell4 - from package: kdelibs

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

On Debian possible default full paths are:

/usr/bin/kshell4 - from package: kdelibs-bin

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

Error in other languages:
kshell4: bevel nie gevind nie
kshell4: comandă negăsită
kshell4: comando não encontrado
kshell4: commande introuvable
kshell4: command not found
kshell4: käsku ei ole
kshell4: không tìm thấy lệnh
kshell4: komanda nerasta
kshell4: Kommando nicht gefunden.
kshell4: kommandot finns inte
kshell4: komut yok
kshell4: nie znaleziono polecenia
kshell4: níor aimsíodh an t-ordú
kshell4: no se encontró la orden
kshell4: no s'ha trobat l'ordre
kshell4: opdracht niet gevonden
kshell4: parancs nem található
kshell4: perintah tidak ditemukan
kshell4: príkaz nenájdený
kshell4: příkaz nenalezen
kshell4: команда не найдена
kshell4: командата не е открита
kshell4: 命令找不到
kshell4: コマンドが見つかりません