unrtf: 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/unrtf - from package: unrtf

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

On Debian possible default full paths are:

/usr/bin/unrtf - from package: unrtf

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

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