wwwifetch: 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/wwwifetch - from package: ifetch-tools

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

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