# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/^.*[^\d\r\n](\d+)/\1/gm;t' <<< "2^64
asdgaf1_hsg534
asdfh23_hsjd12
dgshg_jhfsd86
test
1
testing 1234 testing 1 test4
testing 1234 testing 123"
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for SED, please visit: https://www.gnu.org/software/sed/manual/html_node/The-_0022s_0022-Command.html