tm_r: 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/libexec/TeXmacs/bin/tm_r - from package: TeXmacs

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

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