c4group: 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/c4group - from package: openclonk

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

Error in other languages:
c4group: bevel nie gevind nie
c4group: comandă negăsită
c4group: comando não encontrado
c4group: commande introuvable
c4group: command not found
c4group: käsku ei ole
c4group: không tìm thấy lệnh
c4group: komanda nerasta
c4group: Kommando nicht gefunden.
c4group: kommandot finns inte
c4group: komut yok
c4group: nie znaleziono polecenia
c4group: níor aimsíodh an t-ordú
c4group: no se encontró la orden
c4group: no s'ha trobat l'ordre
c4group: opdracht niet gevonden
c4group: parancs nem található
c4group: perintah tidak ditemukan
c4group: príkaz nenájdený
c4group: příkaz nenalezen
c4group: команда не найдена
c4group: командата не е открита
c4group: 命令找不到
c4group: コマンドが見つかりません