mmcat: 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 Debian possible default full paths are:

/usr/bin/mmcat - from package: sleuthkit

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

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