gnuradio-companion: 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/gnuradio-companion - from package: gnuradio

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

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