Broken pipe error when piping "s3 ls" output to grep -q

[haron]

Confirm by changing [ ] to [x] below to ensure that it's a bug:

• I've gone though the User Guide and the API reference
• I've searched for previous similar issues and didn't find any solution

Describe the bug
[Errno 32] Broken pipe is raised when aws s3 ls output is piped to grep -q and the matching string is found; exit code is 255.

SDK version number
aws-cli/1.18.220 Python/2.7.17 botocore/1.19.60

Platform/OS/Hardware/Device
Linux/4.15.0-134-generic x86_64, Ubuntu 18.04.5 LTS

To Reproduce (observed behavior)
Steps to reproduce the behavior

set -o pipefail; aws s3 ls s3://SOME_S3_PATH | grep -q SOME_STR; echo $?
[Errno 32] Broken pipe
255

Expected behavior
No failure, just a clean exit with code 0.

Additional context
Command grep -q will stop immediately after the first match, and the program which is writing to the pipe will receive SIGPIPE. It is clear, that in case of s3 ls this signal can be ignored.

[kdaily]

Debug shows this:

2021-01-28 20:03:03,419 - MainThread - awscli.clidriver - DEBUG - Exception caught in main()
Traceback (most recent call last):
  File "awscli/clidriver.py", line 457, in main
  File "awscli/customizations/commands.py", line 198, in __call__
  File "awscli/customizations/commands.py", line 191, in __call__
  File "awscli/customizations/s3/subcommands.py", line 509, in _run_main
  File "awscli/customizations/s3/subcommands.py", line 588, in _list_all_objects_recursive
  File "awscli/customizations/s3/subcommands.py", line 566, in _display_page
  File "awscli/customizations/utils.py", line 181, in uni_print
BrokenPipeError: [Errno 32] Broken pipe

[Errno 32] Broken pipe
Exception ignored in: <_io.TextIOWrapper name='<stdout>' mode='w' encoding='utf-8'>
BrokenPipeError: [Errno 32] Broken pipe

[kdaily]

I get an exit code of 120, not 255.

[kdaily]

Looks like we would need to do this to resolve this:

https://docs.python.org/3/library/signal.html#note-on-sigpipe

[bcap]

Fixed this in PR #6303, please review :)

[bcap]

Activelly cc'ing @kdaily as this thread is a bit slow paced and somewhat quiet

[kdaily]

Hi @bcap,

Thanks for the PR, marking this issue to be reviewed.

[nhed]

[FergusFettes]

aws s3 ls s3://XXXX | head -n 1

does the same

currently im buffering it via a tmp file

aws s3 ls s3://XXXX > /tmp/aws-log.txt && cat /tmp/aws-log.txt | head -n 1

but I'm sure this is a more elegant way

[MorayM]

I'm seeing the same behaviour piping to head as @FergusFettes. Also seeing it when piping to grep with -m to limit results, e.g:

aws s3 ls s3://my-bucket/ | grep -m 10 -e 'regex'

I assume the pipe is broken because head is completing before aws s3 ls does, and it's particularly noticeable if the number of items being listed is much greater than the number of items being filtered with head.

I don't know enough about Linux programming in Python to know how to fix it, but I think buffering it through a temp file is probably the simplest fix!

[gregoryb]

I get an exit code of 120, not 255.

Got a similar issue with also exit code = 120. Unable to find an explanation.

[diego-oncoramedical]

My platform differs from the OP but the result seems to be the same.

This works:

aws s3 ls ... | grep ...

If I add -q to grep and there's a regex match, it crashes:

diego@ip-192-168-0-103 ~/Desktop % aws s3 ls s3://bucket/prefix/ | grep -q 'stuff'

[Errno 32] Broken pipe
Exception ignored in: <_io.TextIOWrapper name='<stdout>' mode='w' encoding='utf-8'>
BrokenPipeError: [Errno 32] Broken pipe

If there's no match, the command exits normally with code 1 as expected.

My shell is zsh 5.9 and aws --version gives:

aws-cli/2.15.21 Python/3.11.7 Darwin/23.2.0 source/arm64 prompt/off