wifi: command not found

Have You tried accessing the binary with the full path?

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/wifi - from package: tlp

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