Sed not matching one or more patterns - sed

Question

I have this list of files:
$ more files
one_this_2017_1_abc.txt
two_that_2018_1_abc.txt
three_another_2017_10.abc.txt
four_again_2018_10.abc.txt
five_back_2018_1a.abc.txt
I would like to get this output:
one_this_XXXX_YY_abc.txt
two_that_XXXX_YY_abc.txt
three_another_XXXX_YY.abc.txt
four_again_XXXX_YY.abc.txt
five_back_XXXX_YY.abc.txt
I am trying to remove the year and the bit after the year and replace them with another string--this is to generate test cases.
I can get the year just fine, but it's that one or two character piece after it I can't seem to match.
This should work, right?
~/test_cases
$ cat files | sed -e 's/_[[:digit:]]\{4\}_/_XXXX_/' -e 's/_[[:alnum:]]\{1,2\}_/_YY_/'
one_this_XXXX_YY_abc.txt
two_that_XXXX_YY_abc.txt
three_another_XXXX_10.abc.txt
four_again_XXXX_10.abc.txt
five_back_XXXX_1a.abc.txt
Except it doesn't for the 2 character cases.
$ cat files | sed -e 's/_[[:digit:]]\{4\}_/_XXXX_/' -e 's/_[[:alnum:]]\
{2\}_/_YY_/'
one_this_XXXX_1_abc.txt
two_that_XXXX_1_abc.txt
three_another_XXXX_10.abc.txt
four_again_XXXX_10.abc.txt
five_back_XXXX_1a.abc.txt
Doesn't work for the two character cases either, and this works not at all (but according to the docs it should):
$ cat files | sed -e 's/_[[:digit:]]\{4\}_/_XXXX_/' -e 's/_[[:alnum:]]\+_/_YY_/'
one_YY_XXXX_1_abc.txt
two_YY_XXXX_1_abc.txt
three_YY_XXXX_10.abc.txt
four_YY_XXXX_10.abc.txt
five_YY_XXXX_1a.abc.txt
Other random experiments that don't work:
$ cat files | sed -e 's/_[[:digit:]]\{4\}_/_XXXX_/' -e 's/_[a-zA-Z0-9]\+_/_YY_/'
one_YY_XXXX_1_abc.txt
two_YY_XXXX_1_abc.txt
three_YY_XXXX_10.abc.txt
four_YY_XXXX_10.abc.txt
five_YY_XXXX_1a.abc.txt
$ cat files | sed -e 's/_[[:digit:]]\{4\}_/_XXXX_/' -e 's/_[a-zA-Z0-9]\{1\}_/_YY_/'
one_this_XXXX_YY_abc.txt
two_that_XXXX_YY_abc.txt
three_another_XXXX_10.abc.txt
four_again_XXXX_10.abc.txt
five_back_XXXX_1a.abc.txt
$ cat files | sed -e 's/_[[:digit:]]\{4\}_/_XXXX_/' -e 's/_[a-zA-Z0-9]\{2\}_/_YY_/'
one_this_XXXX_1_abc.txt
two_that_XXXX_1_abc.txt
three_another_XXXX_10.abc.txt
four_again_XXXX_10.abc.txt
five_back_XXXX_1a.abc.txt
Tried with both GNU sed version 4.2.1 under Linux and sed (GNU sed) 4.4 under Cygwin.
And yes, I realize I can pipe this through multiple sed calls to get it to work, but that regex SHOULD work, right?

Answer 1

if your Input_file is same as shown sample then following may help you in same.
sed 's/\([^_]*\)_\([^_]*\)_\(.*_\)\(.*\)/\1_\2_XXXX_YY_\4/g' Input_file
Output will be as follows.
one_this_XXXX_YY_abc.txt
two_that_XXXX_YY_abc.txt
three_another_XXXX_YY_10.abc.txt
four_again_XXXX_YY_10.abc.txt
five_back_XXXX_YY_1a.abc.txt