showriff: 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 CentOS possible default full paths are:

/usr/bin/showriff - from package: xawtv

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/showriff - from package: xawtv-tools

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

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