Merging 2 files records by template

Question

I am trying to use awk to merge two text files in a rather peculiar way, taking two lines from file1, a group of word(s) from file2 (but placed on a separate line), alternating ad infinitum. Groups of word(s) from file2 are delimited by commas. For example:
file1

A Partridge in a Pear Tree
Two Turtle Doves
Three French Hens
Four Calling Birds
Five Gold Rings
Six Geese a-Laying
Seven Swans a-Swimming
Eight Maids a-Milking
Nine Ladies Dancing
Ten Lords a-Leaping
Eleven Pipers Piping
Twelve Drummers Drumming

file2

I was born, the red planet, I am hungry, on Mars
I love frogs, they are so tasty, with gold sun, red ketchup

Output file

A Partridge in a Pear Tree
Two Turtle Doves
I was born
the red planet 
I am hungry
on Mars
Three French Hens
Four Calling Birds
I love frogs
they are so tasty
with gold sun
red ketchup
Five Gold Rings
Six Geese a-Laying
Seven Swans a-Swimming
Eight Maids a-Milking
Nine Ladies Dancing
Ten Lords a-Leaping
Eleven Pipers Piping
Twelve Drummers Drumming

Details:

• In the output file 4 additional lines created from the fields File2 every 2 lines file1
• file1 is split into couplets of two lines, regardless of content
• A line in file2 have 4 number of groups (i.e., 3 number of commas)
• in the output file does not have commas
• A group in file2 have a fixed number of fild
• file1 and file2 may be arbitrarily long
• file2 always less than file1

• File2 fields separated by commas always occur in the same order in each record ( 3,3,3,2) ie., $1 $2 $3, $4 $5 $6, $7 $8 $9, $10 S11

  In the output file to be so arranged

A Partridge in a Pear Tree

Two Turtle Doves

$1 $2 $3

$4 $5 $6

$7 $8 $9

$10 S11

Three French Hens

Four Calling Birds

I love frogs

they are so tasty

with gold sun

red ketchup

Five Gold Rings

Six Geese a-Laying

Seven Swans a-Swimming

Eight Maids a-Milking

Nine Ladies Dancing

Ten Lords a-Leaping

Eleven Pipers Piping

Twelve Drummers Drumming

• Desired behavior when you reach the end of one file but still have data in the other is unspecified- the remaining data (from file1) will be printed without changes

How do I do this?

Answer 1

I believe you have put fifth line from the file1 too early in your example.

If I'm right try this snippet:

awk '(NR+1)%2{print $0;getline<"file2";n=split($0,a,", ");if(n>1)for(i in a)print a[i];next}1' file1

output:

A Partridge in a Pear Tree
Two Turtle Doves
I was born
the red planet
I am hungry
on Mars
Three French Hens
Four Calling Birds
I love frogs
they are so tasty
with gold sun
red ketchup
Five Gold Rings
Six Geese a-Laying
Seven Swans a-Swimming
Eight Maids a-Milking
Nine Ladies Dancing
Ten Lords a-Leaping
Eleven Pipers Piping
Twelve Drummers Drumming

Answer 2

Apart from my comment above if you prefer awk script

awk -F', ' '1;!(NR%2)&&(getline <"file2")>0{$1=$1;print}' OFS='\n' file1

where

• 1 - synonim of {print $0}:
  • condition = true (1),
  • action if do not indicated = default (print),
  • print without arguments = print $0
• !(NR%2) - for even lines:
  • NR - Number of Row(record)
  • % - calculates resedue after dividing by 2,
  • ! - reverse result
• && - logical AND
• getline <"file2" - read line into $0 from file2 and divide it into fields with FieldSeparator indicated as option -F=', ' and return 1 if success.
• $1=$1 - trick to apply OutputFieldSeparator: we have to do something with field(s) otherwise the $0 will printed as it is