irsend: 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/irsend - from package: lirc

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

On Debian possible default full paths are:

/usr/bin/irsend - from package: lirc

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

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