yafc: 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/yafc - from package: yafc

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

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