fslview: 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/fslview - from package: fslview

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

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