rdfpipe: 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/rdfpipe - from package: python-rdflib-tools

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

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