Help with a sed expression

[sentinel166]

Hi, I have sed expressions that p→ßßes me off.
They work well according to regexp101 but not for sed, and it won’t explains why in any meaningful terms.
sed ‘s/(?<!\)(\r|\n)>//g’ essai.md |sed ‘s/(?<!\)(\r|\n)(?!(\r|\n|>))/ /g’|sed ‘s/(\s){2,}/ /g’|sed ‘s/(\r|\n){3,}/\n\n/g’|sed ‘s/\//g’

the first part says:

sed ‘s/(?<!\)(\r|\n)>//g’ essai.md
sed: -e expression n°1, character 20: ) or ) unmatched.

What’s wrong with it ??
essai.md is

> dsfdsfsd
> sdfsdfsdfs\
> sfqsfsqdfd
> mklijmopiuj

> mklijmopiuj

> mklijmopiuj
dsf


sdd\
s

Thanks for your help !

[sradjoker]

what do you want to achieve?? We don’t want this to become a XY problem

[manuel]

The single quotes (') seem to have transformed to other characters.

[manuel]

Didn’t look further at the regex syntax but your file needs to be in the pipe:

cat essai.md | sed 's/(?<!\)(\r|\n)>//g'

Then near the beginning you have
\)
which probably should be just
)

But as @sradjoker said, please tell us what you try to do.

[vlkon]

@sentinel166

according to regexp101

@sentinel166

(?<!)

sed does not support every regex operation. Look-ahead is one of them.
You can check what is supported in the documentation (also with extended regex).
If you need these fancy functions then look for perl or python.

@sentinel166

sed ‘s/(?<!)(\r|\n)>//g’ essai.md |sed ‘s/(?<!)(\r|\n)(?!(\r|\n|>))/ /g’|sed ‘s/(\s){2,}/ /g’|sed ‘s/(\r|\n){3,}/\n\n/g’|sed ‘s///g’

Also, do you know you can make sed replace command more readable if you use different separator than /?
For example sed 's;a/a/a;b/b/b;g' looks better than sed 's/a\/a\/a\//b\/b\/b\//g'.