GNU Awk - don't modify whitespaces

Question

I am using GNU Awk to replace a single character in a file. The file is a single line with varying whitespacing between "fields". After passing through gawk all the extra whitespacing is removed and I end up with single spaces. This is completely unintended and I need it to ignore these spaces and only change the one character I have targeted. I have tried several variations, but I cannot seem to get gawk to ignore these extra spaces.

Since I know this will come up, I read from the end of the line for replacement because the whitespacing is arbitrary/inconsistent in the source file.

Command:

gawk -i inplace -v new=3 'NF {$(NF-5) = new} 1' ~/scripts/tmp_beta_weather_file

Original file example:

2020-07-01 18:29:51.00 C M -11.4  28.9  29      9      23  5.5    000 0 0 00020 044013.77074 1 1 1 3 0 0

Result after command above:

2020-07-01 18:30:51.00 C M -11.8 28.8 29 5 23 5.5 000 0 0 00020 044013.77143 3 1 1 3 0 0

Answer 1

it might be easier with sed

sed -E 's/([^ ]+)(( [^ ]+){5})$/3\2/' file

test and add -i for in-place edit.