spatialite-gui: 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/spatialite-gui - from package: spatialite-gui

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

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