fsharpi: 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 Debian possible default full paths are:

/usr/bin/fsharpi - from package: fsharp

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

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