ddcpci: command not found

Have You tried accessing the binary with the full path?

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/ddcpci - from package: ddccontrol

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