I want to clean strings that may contain garbage at the end, always separated by a forward slash / and if there is no garbage, there is no separator.

Example > expected output

Foo/Bar > Foo 
Foobar > Foobar

I tried several versions like this one to extract the payload only, none of the worked:

(.*)\/.*

(.*)?\/.*

(.*)?\/*.*

And so on. Problem is: i always only get the first or second line to match.

What would be the correct expression to extract the wanted information?

CodePudding user response：

Your first and second pattern capture till before the first / so that will not give a match for the third line as there is no / present.

The third pattern matches the whole line as the /* matches an optional forward slash, so the capture group will match the whole line, and the .* will not match any characters any more as the capture group is already at the end of the line.

You could write the pattern with a capture group for 1 or more word characters as the first part, and an optional second part starting the match from / till the end of the string.

In the replacement you can use the first capture group.

^(\w )(?:\/.*)?$

• ^ Start of string
• (\w ) Capture 1 word characters in group 1
• (?:\/.*)? Optionally match / and the rest of the line (to be removed after the replacement)
• $ End of string

See a regex demo.

There is no language listed, but an example using JavaScript:

const regex = /^(\w )(?:\/.*)?$/m;
const str = `Foo/Bar
Foobar`;
const result = str.replace(regex, "$1");
console.log(result);

<iframe name="sif1" sandbox="allow-forms allow-modals allow-scripts" frameborder="0"></iframe>

---

Example using Python

import re

regex = r"^(\w )(?:\/.*)?$"
test_str = ("Foo/Bar\n"
    "Foobar")
result = re.sub(regex, r'\1', test_str, 0, re.MULTILINE)

if result:
    print (result)

Output

Foo
Foobar

Python demo

CodePudding user response：

You can use replace here as:

const cleanString = (str) => str.replace(/\/.*/, "");

console.log(cleanString("Foo/Bar"));
console.log(cleanString("Foobar"));

<iframe name="sif2" sandbox="allow-forms allow-modals allow-scripts" frameborder="0"></iframe>

CodePudding user response：

You can try doing a regex.split on / and select the first element from the list. For example in python:

import regex as re

new_string = re.split('/',string)[0]

CodePudding user response：

This task doesn't need the power of regex, you need to split on the first slash, e.g. in Python:

test_string.split('/', 1)[0]

I think the reason your regex doesn't work is that Foobar has no / to match on. So for regex you need to handle none, one, or many slashes. Again, in Python:

>>> test = ['foobar', 'foo/bar', 'foo/bar/baz']
>>> for s in t:
    print(re.findall('^(.*?)(?=/|$)', s))
        
['foobar']
['foo']
['foo']

The regex says: from the start of the string, group all characters (non-greedy) until either a slash or the end of the string.