ffindex_get: command not found

Have You tried accessing the binary with the full path?

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/ffindex_get - from package: ffindex

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