gsi: 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/gsi - from package: gambit-c
/usr/lib64/gambit-c/bin/gsi - from package: gambit-c

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

On Debian possible default full paths are:

/usr/bin/gsi - from package: gambc

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

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