xsupplicant: 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/sbin/xsupplicant - from package: xsupplicant

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

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