httrack: 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/httrack - from package: httrack

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

On Debian possible default full paths are:

/usr/bin/httrack - from package: httrack

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

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