markers3.txt: 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/share/doc/r-cran-qtl/examples/bin/test/std/markers3.txt - from package: r-cran-qtl

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

Error in other languages:
markers3.txt: bevel nie gevind nie
markers3.txt: comandă negăsită
markers3.txt: comando não encontrado
markers3.txt: commande introuvable
markers3.txt: command not found
markers3.txt: käsku ei ole
markers3.txt: không tìm thấy lệnh
markers3.txt: komanda nerasta
markers3.txt: Kommando nicht gefunden.
markers3.txt: kommandot finns inte
markers3.txt: komut yok
markers3.txt: nie znaleziono polecenia
markers3.txt: níor aimsíodh an t-ordú
markers3.txt: no se encontró la orden
markers3.txt: no s'ha trobat l'ordre
markers3.txt: opdracht niet gevonden
markers3.txt: parancs nem található
markers3.txt: perintah tidak ditemukan
markers3.txt: príkaz nenájdený
markers3.txt: příkaz nenalezen
markers3.txt: команда не найдена
markers3.txt: командата не е открита
markers3.txt: 命令找不到
markers3.txt: コマンドが見つかりません