xcos: 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/xcos - from package: scilab

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