Bash: How to use sed to remove all characters except letters and numbers?

Question

First off, I'm still learning about regular expression, I have googled about this but still doesn't work.

How do I remove all characters except letters and numbers in a variable with sed? For example I have this text file:

MytextOnly !@#!text@@32423#@$text#%$#text%#t23432ext$32342%^-_+-=-_++_;:"'][}}{|\/

How do I show only letters and numbers?

Solution 1

You can use:

sed 's/[^[:alnum:]]\+//g' file
MytextOnlytext32423texttextt23432ext32342

[^[:alnum:]] property will find all non-alphanumerical characters.

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EDIT: Based on comments below:

sed 's~[^[:alnum:]/]\+~~g' file
MytextOnlytext32423texttextt23432ext32342/

Solution 2

Using grep

grep -o '[[:alnum:]]' file

agree, no the perfect output, but everything is there

Using tr

$ tr -d -c '[:alnum:]' < file
MytextOnlytext32423texttextt23432ext32342

If you also want to keep forward slashes:

$ tr -d -c '[:alnum:]/' < file
MytextOnlytext32423texttextt23432ext32342/

For a python solution, see https://stackoverflow.com/a/5843560/297323