mash: 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/mash - from package: mash

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

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