expect: 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/expect - from package: expect

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

On Debian possible default full paths are:

/usr/bin/expect - from package: expect

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

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