dispcalGUI-curve-viewer: 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/dispcalGUI-curve-viewer - from package: dispcalgui

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

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