can you help

i am merging 2 files together and saving to a third file with awk
and its working with this code

awk 'OFS="";NR==FNR{a[FNR]=$0;next} {print a[FNR],"\n","\b",$0}' file1 file2 > file3

the problem is in file3 when its saved
i get a small square at the start of every 2nd line (see picture)

i need to get rid of the squares
whats wrong with the code ?

thanks

File 1

AAAA
BBBB
CCCC

File 2

XXXX
YYYY
ZZZZ

File 3

AAAA
XXXX
BBBB
YYYY
CCCC
ZZZZ

Why are you printing a backspace character ( \b ) ? Just leave it out.

--
As a matter of efficiency, set OFS="" in the BEGIN section...
In fact, you do not need it at all if your use print a[FNR] "\n" $0

@Scrutinizer

i have removed \b from the code

awk 'OFS="";NR==FNR{a[FNR]=$0;next} {print a[FNR],"\n",$0}' file1 file2 > file3

and the squares have gone

thank you

This is exactly what paste is for:

paste -d"\n" file[12]
AAAA
XXXX
BBBB
YYYY
CCCC
ZZZZ

If you go with awk instead of RudiC's suggestion of paste you can still simplify your code (as Scrutinizer suggested) and get exactly the same output:

awk 'NR==FNR{a[FNR]=$0;next} {print a[FNR] "\n" $0}' file1 file2 > file3

(Note that the commas in your print statement are the only things that use the value of OFS in your script.)

Or

awk 'NR==FNR{a[FNR]=$0;next} {print a[FNR]} 1' file1 file2 > file3

Or:

awk '1;getline<f>0' f=file2 file1 > file3