frog: 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/frog - from package: frog

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

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