pcl_normal_estimation: 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/pcl_normal_estimation - from package: pcl-tools

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

On Debian possible default full paths are:

/usr/bin/pcl_normal_estimation - from package: pcl-tools

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

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