Replace last occurrence of a character in a field with awk

Question

I\'m trying to replace the last occurrence of a character in a field with awk. Given is a file like this one:

John,Doe,Abc fgh 123,Abc
John,Doe,Ijk-nop 45D,D         


        

Answer 1

With GNU awk for gensub():

$ awk 'BEGIN{FS=OFS=","} {$3=gensub(/(.*) /,"\\1,","",$3)}1' file
John,Doe,Abc fgh,123,Abc
John,Doe,Ijk-nop,45D,Def
John,Doe,Qr s Uvw,6,Ghi

Get the book Effective Awk Programming by Arnold Robbins.

Very well-written question btw!

Answer 2

Here is a short awk

awk '{$NF=RS$NF;sub(" "RS,",")}1' file
John,Doe,Abc fgh,123,Abc
John,Doe,Ijk-nop,45D,Def
John,Doe,Qr s Uvw,6,Ghi

Updated due to Eds comment.

Or you can use the rev tools.

rev file | sed 's/ /,/' | rev
John,Doe,Abc fgh,123,Abc
John,Doe,Ijk-nop,45D,Def
John,Doe,Qr s Uvw,6,Ghi

Revers the line, then replace first space with ,, then revers again.