Signals in F#

Here’s the translation of the Go code example to F# with explanations in Markdown format suitable for Hugo:

In F#, we can handle signals using the System.Console.CancelKeyPress event. This example demonstrates how to handle the SIGINT (Ctrl+C) signal in an F# program.

open System
open System.Threading

// Create a ManualResetEvent to signal when the program should exit
let exitEvent = new ManualResetEvent(false)

// Set up the event handler for Ctrl+C
Console.CancelKeyPress.Add(fun args ->
    printfn "\nInterrupt received"
    args.Cancel <- true  // Prevent the process from terminating immediately
    exitEvent.Set() |> ignore  // Signal the main thread to exit
)

// Main function
[<EntryPoint>]
let main argv =
    printfn "Awaiting signal"
    
    // Wait for the exit signal
    exitEvent.WaitOne() |> ignore
    
    printfn "Exiting"
    0  // Return 0 to indicate successful execution

This F# program sets up a signal handler for the SIGINT signal (usually triggered by pressing Ctrl+C). Here’s how it works:

1. We create a ManualResetEvent called exitEvent. This will be used to signal when the program should exit.

2. We add an event handler to Console.CancelKeyPress. This event is raised when the user presses Ctrl+C.

3. In the event handler:

   • We print a message indicating that an interrupt was received.
   • We set args.Cancel to true to prevent the process from terminating immediately.
   • We signal the exitEvent to let the main thread know it’s time to exit.

4. In the main function:

   • We print a message saying we’re awaiting a signal.
   • We wait on the exitEvent using WaitOne(). This blocks the main thread until the event is signaled.
   • Once the event is signaled (i.e., after Ctrl+C is pressed), we print an “Exiting” message and the program terminates.

When we run this program, it will block waiting for a signal. By typing Ctrl+C, we can send a SIGINT signal, causing the program to print “Interrupt received” and then exit.

$ dotnet run
Awaiting signal
^C
Interrupt received
Exiting

This example demonstrates a basic approach to handling signals in F#. While it doesn’t provide the same level of granularity as Go’s signal handling (e.g., distinguishing between SIGINT and SIGTERM), it shows how to gracefully handle interrupts in an F# program.