sgmlpre: 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/sgmlpre - from package: linuxdoc-tools

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

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