ag++: 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 Debian possible default full paths are:

/usr/bin/ag++ - from package: aspectc++

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