xcfview: 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/xcfview - from package: xcftools

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

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