ptex: 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/ptex - from package: texlive-east-asian

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

On Debian possible default full paths are:

/usr/bin/ptex - from package: texlive-binaries

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

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