listings-ext: 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/listings-ext - from package: texlive-extra-utils

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

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