xdg-open: 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/xdg-open - from package: xdg-utils

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

On Debian possible default full paths are:

/usr/bin/xdg-open - from package: xdg-utils

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

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