gstat-fb: 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/gstat-fb - from package: firebird

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

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