FreeFem++: 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/FreeFem++ - from package: freefem++

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

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