tcpbug: 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/tcpbug - from package: tcputils

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

On Debian possible default full paths are:

/usr/bin/tcpbug - from package: tcputils

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

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