ytobin-gfortran: 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/ytobin-gfortran - from package: patchy-gfortran

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

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