pstops: 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/pstops - from package: psutils

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

On Debian possible default full paths are:

/usr/bin/pstops - from package: psutils

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

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