antlr3: 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 Debian possible default full paths are:

/usr/bin/antlr3 - from package: antlr3

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

Error in other languages:
antlr3: bevel nie gevind nie
antlr3: comandă negăsită
antlr3: comando não encontrado
antlr3: commande introuvable
antlr3: command not found
antlr3: käsku ei ole
antlr3: không tìm thấy lệnh
antlr3: komanda nerasta
antlr3: Kommando nicht gefunden.
antlr3: kommandot finns inte
antlr3: komut yok
antlr3: nie znaleziono polecenia
antlr3: níor aimsíodh an t-ordú
antlr3: no se encontró la orden
antlr3: no s'ha trobat l'ordre
antlr3: opdracht niet gevonden
antlr3: parancs nem található
antlr3: perintah tidak ditemukan
antlr3: príkaz nenájdený
antlr3: příkaz nenalezen
antlr3: команда не найдена
antlr3: командата не е открита
antlr3: 命令找不到
antlr3: コマンドが見つかりません