grep: invalid option -- P

[JonasGoetz01]

Actual behavior
When trying to grep some content during a ci pipeline I get this error:

grep: invalid option -- P
BusyBox v1.32.0 (2020-12-03 00:49:17 UTC) multi-call binary.
Usage: grep [-HhnlLoqvsrRiwFE] [-m N] [-A/B/C N] PATTERN/-e PATTERN.../-f FILE [FILE]...
Search for PATTERN in FILEs (or stdin)
	-H	Add 'filename:' prefix
	-h	Do not add 'filename:' prefix
	-n	Add 'line_no:' prefix
	-l	Show only names of files that match
	-L	Show only names of files that don't match
	-c	Show only count of matching lines
	-o	Show only the matching part of line
	-q	Quiet. Return 0 if PATTERN is found, 1 otherwise
	-v	Select non-matching lines
	-s	Suppress open and read errors
	-r	Recurse
	-R	Recurse and dereference symlinks
	-i	Ignore case
	-w	Match whole words only
	-x	Match whole lines only
	-F	PATTERN is a literal (not regexp)
	-E	PATTERN is an extended regexp
	-m N	Match up to N times per file
	-A N	Print N lines of trailing context
	-B N	Print N lines of leading context
	-C N	Same as '-A N -B N'
	-e PTRN	Pattern to match
	-f FILE	Read pattern from file

Expected behavior
the grep command should get the version number out of a specific file

To Reproduce
Steps to reproduce the behavior:

1. Start a CI/CD pipeline with the latest gcr.io/kaniko-project/executor:debug image
2. Use a grep -Pzo command like provided later.

Additional Information

• Dockerfile
  There isn't a specific Dockerfile needed to reproduce that error.

Example File
Example yaml

version/number:22.3.1

Example grep command inside the pipeline

grep -Pzo 'version/number:(.)*' example-file.yml | cut -d ":" -f 2

Description	Yes/No
Please check if this is a new feature you are proposing
Please check if the build works in docker but not in kaniko
Please check if this error is seen when you use --cache flag
Please check if your Dockerfile is a multistage Dockerfile

[imjasonh]

Did this work in a previous version of Kaniko?

This sounds like busybox (which Kaniko's :debug image is based on to provide a shell and userspace) doesn't support grep -P. I'm not sure there's a lot we can do about it, unless this is a recent regression.

[JonasGoetz01]

No I don't know if that worked in an earlier version

[imjasonh]

Thanks, that's helpful to know.

In that case, I think this is working as intended -- the :debug image is based on busybox, which supports certain options for grep, of which -P is not one.