ptksh: 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/ptksh - from package: perl-Tk

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

On Debian possible default full paths are:

/usr/bin/ptksh - from package: perl-Tk

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

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