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Asked: 2026-05-13T23:44:48+00:00

I was hoping someone could answer my quick question as I am going nuts!

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I was hoping someone could answer my quick question as I am going nuts!

I have recently started learning regular expressions in my Java programming however am a little confused how to get certain features to work correctly directly in BASH. For example, the following code is not working as I think it should.

echo 2222 | grep '2\{2\}'

I am expecting it to return:

22

I have tried variations of it including:

echo 2222 | grep '2{2}'
echo 2222 | grep -P '2\{2\}'
echo 2222 | grep -E '2\{2\}'

However I am completely out of ideas. I’m sure this is a simple parameter / syntax fix and would love some help! P.S I’ve done tons of googling and every reference I find does not work in BASH; regex’s can run on so many different platforms and engines =/

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1 Answer

  1. Editorial Team
    echo 2222 | grep -E '2{2}'
2222

    The regex will pattern match on the line, and either print out the whole line (2222) if it matches, or nothing if it doesn’t.

    It will NOT pull out a portion of the output. For that, you want something like sed:

    echo 2222 | sed 's/.*\(2\{2\}\).*/\1/'
22
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