ptx: command not found

Have You tried accessing the binary with the full path?

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/ptx - from package: coreutils

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

On Debian possible default full paths are:

/usr/bin/ptx - from package: coreutils

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