Is it possible to capture a Ctrl C signal and run a cleanup function in a defer fashion

Question

I want to capture the Ctrl C  SIGINT  signal sent from the console and print out some partial run totals   Is this possible in Golang   Note  When I first posted the question I was confused about Ctrl C being SIGTERM instead of SIGINT

User · Answer

This is another version which work in case you have some tasks to cleanup. Code will leave clean up process in their method.

package main

import (
    "fmt"
    "os"
    "os/signal"
    "syscall"

)



func main() {

    _,done1:=doSomething1()
    _,done2:=doSomething2()

    //do main thread


    println("wait for finish")
    <-done1
    <-done2
    fmt.Print("clean up done, can exit safely")

}

func doSomething1() (error, chan bool) {
    //do something
    done:=make(chan bool)
    c := make(chan os.Signal, 2)
    signal.Notify(c, os.Interrupt, syscall.SIGTERM)
    go func() {
        <-c
        //cleanup of something1
        done<-true
    }()
    return nil,done
}


func doSomething2() (error, chan bool) {
    //do something
    done:=make(chan bool)
    c := make(chan os.Signal, 2)
    signal.Notify(c, os.Interrupt, syscall.SIGTERM)
    go func() {
        <-c
        //cleanup of something2
        done<-true
    }()
    return nil,done
}

in case you need to clean main function you need to capture signal in main thread using go func() as well.

User · Answer

Just for the record if somebody needs a way to handle signals on Windows  I had a requirement to handle from prog A calling prog B through os exec but prog B never was able to terminate gracefully because sending signals through ex  cmd Process Signal syscall SIGTERM  or other signals are not supported on Windows  The way I handled is by creating a temp file as a signal ex   signal term through prog A and prog B needs to check if that file exists on interval base  if file exists it will exit the program and handle a cleanup if needed  I m sure there are other ways but this did the job

User · Answer

Death is a simple library that uses channels and a wait group to wait for shutdown signals  Once the signal has been received it will then call a close method on all of your structs that you want to cleanup

User · Answer

To add slightly to the other answers  if you actually want to catch SIGTERM  the default signal sent by the kill command   you can use syscall SIGTERM in place of os Interrupt  Beware that the syscall interface is system-specific and might not work everywhere  e g  on windows   But it works nicely to catch both   c    make chan os Signal  2  signal Notify c  os Interrupt  syscall SIGTERM

User · Answer

There were  at time of posting  one or two little typos in the accepted answer above  so here s the cleaned up version   In this example I m stopping the CPU profiler when receiving Ctrl C      capture ctrl c and stop CPU profiler                             c    make chan os Signal  1                                         signal Notify c  os Interrupt                                       go func                                                               for sig    range c                                                    log Printf  captured  v  stopping profiler and exiting     sig      pprof StopCPUProfile                                                os Exit 1

User · Answer

You can have a different goroutine that detects syscall SIGINT and syscall SIGTERM signals and relay them to a channel using signal Notify  You can send a hook to that goroutine using a channel and save it in a function slice  When the shutdown signal is detected on the channel  you can execute those functions in the slice  This can be used to clean up the resources  wait for running goroutines to finish  persist data  or print partial run totals   I wrote a small and simple utility to add and run hooks at shutdown  Hope it can be of help    https   github com ankit-arora go-utils blob master go-shutdown-hook shutdown-hook go  You can do this in a  defer  fashion   example for shutting down a server gracefully    srv     amp http Server    go shutdown hook ADD func         log Println  shutting down server       srv Shutdown nil      log Println  shutting down server-done       l  err    net Listen  tcp     3090    log Println srv Serve l    go shutdown hook Wait

User · Answer

All of the above seem to work when spliced in  but gobyexample s signals page has a really clean and complete example of signal capturing  Worth adding to this list

User · Answer

This works     package main  import        fmt       os       os signal       syscall       time     or  runtime     func cleanup         fmt Println  cleanup      func main         c    make chan os Signal      signal Notify c  os Interrupt  syscall SIGTERM      go func              lt -c         cleanup           os Exit 1               for           fmt Println  sleeping              time Sleep 10   time Second     or runtime Gosched   or similar per  misterbee

User · Answer

look at the example When we run this program it will block waiting for a signal  By typing ctrl-C  which the terminal shows as  C  we can send a SIGINT signal  causing the program to print interrupt and then exit  signal  Notify registers the given channel to receive notifications of the specified signals  package main  import        quot fmt quot       quot os quot       quot os signal quot       quot syscall quot     func main          sig    make chan os Signal  1      done    make chan bool  1       signal Notify sig  syscall SIGINT  syscall SIGTERM       go func             sig     lt -sig         fmt Println           fmt Println sig          done  lt - true          fmt Println  quot ctrl c quot                fmt Println  quot awaiting signal quot        lt -done     fmt Println  quot exiting quot      detect HTTP request cancel   package main  import        quot fmt quot       quot net http quot       quot time quot     func main          mux    http NewServeMux       mux HandleFunc  quot  path quot   func writer http ResponseWriter  request  http Request             time Sleep time Second   5           select           case  lt -time After time Millisecond   10                fmt Println  quot started quot               return         case  lt -request Context   Done                fmt Println  quot canceled quot                         http ListenAndServe  quot  8000 quot   mux

User · Answer

You can use the os signal package to handle incoming signals  Ctrl C is SIGINT  so you can use this to trap os Interrupt   c    make chan os Signal  1  signal Notify c  os Interrupt  go func        for sig    range c              sig is a  C  handle it             The manner in which you cause your program to terminate and print information is entirely up to you

[signals] Is it possible to capture a Ctrl+C signal and run a cleanup function, in a "defer" fashion?

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