# Bug in Starting background jobs #at7?

**URL:** <https://forum.codecrafters.io/t/bug-in-starting-background-jobs-at7/16026>\
**Category:** Bug Reports\
**Tags:** challenge:shell\
**Created:** [April 5, 2026, 8:01pm UTC](https://forum.codecrafters.io/t/bug-in-starting-background-jobs-at7/16026 "2026-04-05T20:01:54Z")\
**Posts on this page:** 11\
**Page:** 1

<div class="post-metadata">

**Author:** ![fly-434](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/fly-434/32/32_2.png) [@fly-434](https://forum.codecrafters.io/u/fly-434)\
**Post date:** [April 5, 2026, 8:01pm UTC](https://forum.codecrafters.io/t/bug-in-starting-background-jobs-at7/16026/1 "2026-04-05T20:01:54Z")

</div>

I’m stuck on Stage #AT7 and I think there’s a bug in the testing code.

The process is running in background, I can look up the pid in ps.

My shell:

> $ sleep 15000 &  
> [1] 90531

Bash:

> $ ps aux | grep 90531  
> dom 90531 0.0 0.0 5572 2140 pts/3 S+ 21:57 0:00 sleep 15000  
> dom 90536 0.0 0.0 6520 2388 pts/0 S+ 21:57 0:00 grep --color=always 90531

It is correctly running in background. Yet, the test fails here:

> [tester::#AT7] Running tests for Stage #AT7 (Background Jobs - Starting background jobs)  
> [tester::#AT7] Running ./your\_program.sh  
> [your-program] $ sleep 500 &  
> [your-program] [1] 44  
> [tester::#AT7] Could not find process with PID 44  
> [tester::#AT7] Test failed

I think the 500 ms sleep may be too short and my machine too slow, so the process terminates before the test has had a chance to verify it’s running. Just a guess.

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<div class="post-metadata">

**Author:** ![fly-434](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/fly-434/32/32_2.png) [@fly-434](https://forum.codecrafters.io/u/fly-434)\
**Post date:** [April 7, 2026, 6:11pm UTC](https://forum.codecrafters.io/t/bug-in-starting-background-jobs-at7/16026/3 "2026-04-07T18:11:09Z")

</div>

Oh that’s 500 seconds, not ms. Still can’t work around the issue though.  
Anyone ever hit something similar?

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<div class="post-metadata">

**Author:** ![senevoldsen](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/senevoldsen/32/6460_2.png) [@senevoldsen](https://forum.codecrafters.io/u/senevoldsen)\
**Post date:** [April 7, 2026, 6:14pm UTC](https://forum.codecrafters.io/t/bug-in-starting-background-jobs-at7/16026/4 "2026-04-07T18:14:53Z")

</div>

You are probably going to have to show us you process launching code to see what happens.

Does the test actually take 500s? Or does it fail sooner than that?

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<div class="post-metadata">

**Author:** ![senevoldsen](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/senevoldsen/32/6460_2.png) [@senevoldsen](https://forum.codecrafters.io/u/senevoldsen)\
**Post date:** [April 7, 2026, 6:27pm UTC](https://forum.codecrafters.io/t/bug-in-starting-background-jobs-at7/16026/5 "2026-04-07T18:27:06Z")

</div>

Also, is the spawned process a direct child of your Shell, or are there any intermediary processes spawned too?

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<div class="post-metadata">

**Author:** ![fly-434](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/fly-434/32/32_2.png) [@fly-434](https://forum.codecrafters.io/u/fly-434)\
**Post date:** [April 7, 2026, 6:31pm UTC](https://forum.codecrafters.io/t/bug-in-starting-background-jobs-at7/16026/6 "2026-04-07T18:31:53Z")

</div>

It fails sooner. It’s a direct child. Let me paste the code:

```auto
def run_executable(command_path: str, user_input: UserInput) -> None:
    pid = os.fork()
    if pid == 0:
        if user_input.is_background:
            # Create new session for the child process, detaching it from the
            # parent's terminal and process group: signals sent to the shell's
            # process group won't reach the background child.
            os.setsid()
            # Redirect stdin to /dev/null to prevent the child from blocking or
            # dying on a closed pipe.
            devnull = os.open("/dev/null", os.O_RDONLY)
            os.dup2(devnull, 0)
            os.close(devnull)

        if user_input.stdout_file:
            mode = (
                os.O_WRONLY
                | os.O_CREAT
                | (os.O_APPEND if user_input.stdout_append else os.O_TRUNC)
            )
            stdout_fd = os.open(user_input.stdout_file, mode, 0o644)
            os.dup2(stdout_fd, sys.stdout.fileno())
            os.close(stdout_fd)

        if user_input.stderr_file:
            mode = (
                os.O_WRONLY
                | os.O_CREAT
                | (os.O_APPEND if user_input.stderr_append else os.O_TRUNC)
            )
            stderr_fd = os.open(user_input.stderr_file, mode, 0o644)
            os.dup2(stderr_fd, sys.stderr.fileno())
            os.close(stderr_fd)

        try:
            os.execv(command_path, [user_input.command] + user_input.parameters)
        except OSError as e:
            os._exit(127)
    else:
        if user_input.is_background:
            job_number = 1
            if jobs:
                last_key = max(jobs.keys())
                job_number = last_key + 1
            jobs[job_number] = pid
            outln(f"[{job_number}] {pid}")
        else:
            os.waitpid(pid, 0)

```

even simplifying the code to:

```python
def run_executable(command_path: str, user_input: UserInput) -> None:
    pid = os.fork()
    if pid == 0:
        os.execv(command_path, [user_input.command] + user_input.parameters)
    else:
        if user_input.is_background:
            job_number = 1
            if jobs:
                last_key = max(jobs.keys())
                job_number = last_key + 1
            jobs[job_number] = pid
            outln(f"[{job_number}] {pid}")
        else:
            os.waitpid(pid, 0)

```

causes the same error

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<div class="post-metadata">

**Author:** ![senevoldsen](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/senevoldsen/32/6460_2.png) [@senevoldsen](https://forum.codecrafters.io/u/senevoldsen)\
**Post date:** [April 7, 2026, 6:49pm UTC](https://forum.codecrafters.io/t/bug-in-starting-background-jobs-at7/16026/7 "2026-04-07T18:49:48Z")

</div>

I assume `command_path` is the fully resolved path to the command, e.g. `/usr/bin/sleep` and not just `sleep`? I guess it would have to be otherwise you example earlier would fail.

Yeah, unless the child crashes really quickly (somehow finding a different sleep or something), I can’t see the issue. Try adding a 1 second sleep in Python before you output the job number and PID in the parent; I can’t see and doubt there is a race issue there, but quick experiment to try.

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<div class="post-metadata">

**Author:** ![senevoldsen](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/senevoldsen/32/6460_2.png) [@senevoldsen](https://forum.codecrafters.io/u/senevoldsen)\
**Post date:** [April 7, 2026, 7:18pm UTC](https://forum.codecrafters.io/t/bug-in-starting-background-jobs-at7/16026/8 "2026-04-07T19:18:12Z")

</div>

Can you verify, at least locally, that ppid and pid are as expected for both shell and child?

`ps -o pid,ppid,cmd`

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<div class="post-metadata">

**Author:** ![fly-434](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/fly-434/32/32_2.png) [@fly-434](https://forum.codecrafters.io/u/fly-434)\
**Post date:** [April 9, 2026, 5:15pm UTC](https://forum.codecrafters.io/t/bug-in-starting-background-jobs-at7/16026/9 "2026-04-09T17:15:11Z")

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Yes: command\_path=‘/bin/sleep’.

Adding a 1 second sleep before outputting the job number/pid didn’t help.

From my shell:

> $ sleep 15 &  
> [1] 50410

From bash:

> ps -o pid,ppid,cmd -p 50410  
> PID PPID CMD  
> 50410 50348 sleep 15

> $ ps -o pid,ppid,cmd -p 50348  
> PID PPID CMD  
> 50348 1484 python3 app/main.py

Even using pstree, I don’t see anything anomalous (apart from some zombie processes I need to reap):

> ```
> |-tmux: server(1483)-+-bash(1484)---python3(50348)-+-sleep(50350)
> | | |-sleep(50410)
> | | `-sleep(50631)
> 
> ```

I don’t know what else to try. Can I find somewhere the code that checks for the presence of the child process or is it closed source?

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<div class="post-metadata">

**Author:** ![andy1li](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/andy1li/32/10_2.png) [@andy1li](https://forum.codecrafters.io/u/andy1li)\
**Post date:** [April 10, 2026, 12:05am UTC](https://forum.codecrafters.io/t/bug-in-starting-background-jobs-at7/16026/10 "2026-04-10T00:05:55Z")

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Hey @fly-434, this is an issue on our end.

We’re investigating it now and will share an update as soon as we have a fix

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<div class="post-metadata">

**Author:** ![fly-434](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/fly-434/32/32_2.png) [@fly-434](https://forum.codecrafters.io/u/fly-434)\
**Post date:** [April 10, 2026, 7:42pm UTC](https://forum.codecrafters.io/t/bug-in-starting-background-jobs-at7/16026/11 "2026-04-10T19:42:19Z")

</div>

Thanks for looking into this. Let me know if I can help in any way

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<div class="post-metadata">

**Author:** ![andy1li](https://yyz1.discourse-cdn.com/flex003/user_avatar/forum.codecrafters.io/andy1li/32/10_2.png) [@andy1li](https://forum.codecrafters.io/u/andy1li)\
**Post date:** [April 14, 2026, 11:08am UTC](https://forum.codecrafters.io/t/bug-in-starting-background-jobs-at7/16026/12 "2026-04-14T11:08:55Z")

</div>

Quick update: we’ve pushed a fix in [this PR](https://github.com/codecrafters-io/shell-tester/pull/280).

Could you give it another try and let me know how it goes? @fly-434