delve: Unable to read stdin input in debug mode

I am a go language enthusiast and I am just getting started. Here is my question: In debug mode, the program is blocked in stdin and cannot be entered.

What version of Delve are you using (dlv version)?

Delve Debugger
Version: 1.0.0
Build: 86120a3b4038318b08c2898059733a7bf1499ee5

What version of Go are you using? (go version)?

go version go1.9.3 darwin/amd64

What operating system and processor architecture are you using?

Darwin yiji.local 17.4.0 Darwin Kernel Version 17.4.0: Sun Dec 17 09:19:54 PST 2017; root:xnu-4570.41.2~1/RELEASE_X86_64 x86_64

What did you do? In debug mode, the program is blocked in stdin and cannot be entered.
What did you expect to see? The program receives input and the debug runs normally.
What did you see instead? Here is my simple code :

package main

import (
	"bufio"
	"os"
	"fmt"
)

func main()  {
	input := bufio.NewScanner(os.Stdin)
	words := make(map[string]int)
	for input.Scan() {
		fmt.Println("Received:" + input.Text())
		if len(input.Text()) <= 0 {
			break
		}
		words[input.Text()]++
	}

	for word, n := range words {
		if n > 1 {
			fmt.Printf("%d %s\n", n, word)
		}
	}
}

Is this a bug?

About this issue

Original URL
State: closed
Created 6 years ago
Reactions: 8
Comments: 16 (4 by maintainers)

Most upvoted comments

Hello Delve Developers, I would like to note I’ve run into this issue in my own development efforts. Being able to debug with console input is a fundamental basic tool in writing applications. An attempt to look into this issue again would be appreciated.

Regards, Aaron

+63

AaronViviano on Dec 12, 2018

It works, thanks, This treatment is not elegant, will it improve in the future?

Highly unlikely. Debugging like this is of little practical use.

+59

aarzilli on Jul 23, 2018

The argument I’ve read on slack is not correct in my opinion.

imho it’s a bad idea to interact with the program you are debugging, you should set up something to reproduce the problem automatically

What happens if a program you’ve made just has a bug and you want to do the same as the user did? You start the program (via VSC) with debug, but… the debugger stops when the user input is wanted. I would love to see a fix for this (and not a workaround)

+37

marcel-aan-zee on Oct 22, 2019

I think we do need to fix this issue.

It’s really useful in some situations.
😦

+15

BlackWaters on Jul 29, 2021

So far the only supported way to debug a program like this is to start a headless instance in one terminal:

dlv --headless debug yourprogram.go

This will print something like this:

API server listening at: 127.0.0.1:XYZ

then in another terminal do:

dlv connect :XYZ

Input for delve will go in the second terminal, input for your program will go in the first one.

Duplicate of #65

+14

aarzilli on Jul 23, 2018

Highly unlikely. Debugging like this is of little practical use.

I suggest you examine the number of downvotes this comment has gotten. As a programmer of 35-odd years, I can assure you that you are quite mistaken. Note that people write different types of programs. Maybe you may not find yourself writing such code, but this idiom is what UNIX was built upon: piping data from one program to another. In my case, I’m debugging a protocol buffers generator plugin that communicates via a pipe.

daniel-santos on Oct 25, 2020

Maybe you may not find yourself writing such code, but this idiom is what UNIX was built upon: piping data from one program to another. In my case, I’m debugging a protocol buffers generator plugin that communicates via a pipe.

You can do that with -r and process substitution. See 7555d1c06339e51a4f1e2d7a62dc9c44745e10b7

aarzilli on Oct 25, 2020