fst-infl: 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/fst-infl - from package: sfst

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