UNIX for Beginners Questions & Answers

Yes, initially, I did not notice it, neither, when you posted the command embedded in the post text. Now that you corrected it, adding code tags, it looks obvious. Posting the input and desired output helps to test as well.
Heading that way.

Some seds accept the xdigit character class.

What Aia suggested works with the sample input, and may be exactly what is wanted (a string of 32 or more hex digits appearing anywhere on an input line without regard to what other characters may be present on the line). But, what was requested in post #4 (Onlye(sic) the lines that are composed with hexadecimal characters.) would be something more like:

Code:

sed -n '/^[a-f0-9A-F]\{1,\}$/p' input

which prints lines that contain one or more hex digits that do not contain any characters that are not hex digits.

If you only want lines that contain exactly 32 hex digits and nothing else, that would be:

Code:

sed -n '/^[a-f0-9A-F]\{32\}$/p' input