grib_to_json: 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/grib_to_json - from package: grib_api

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

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