gct-tool: 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/gct-tool - from package: gwenhywfar

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

On Debian possible default full paths are:

/usr/bin/gct-tool - from package: gwenhywfar-tools

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

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