ffmedit: 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/ffmedit - from package: freefem++

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

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