traffic_line: 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/traffic_line - from package: trafficserver

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

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