urlsnarf: 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/sbin/urlsnarf - from package: dsniff

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

On Debian possible default full paths are:

/usr/sbin/urlsnarf - from package: dsniff

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

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