tmxviewer: 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/tmxviewer - from package: tiled

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

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