ptardiff: 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/ptardiff - from package: perl-Archive-Tar

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

On Debian possible default full paths are:

/usr/bin/ptardiff - from package: perl

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

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