six-script: 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/lib64/gambit-c/bin/six-script - from package: gambit-c

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

On Debian possible default full paths are:

/usr/bin/six-script - from package: gambc

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

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