nicholas@mordor:~/regex$ 
nicholas@mordor:~/regex$ cat input.txt 


a : one
b : two
c : three
d : four
a : first
b : second
c : third
d : fourth

nicholas@mordor:~/regex$ 
nicholas@mordor:~/regex$ cat out.txt 



a,one,b,two,c,three,d,four
a,first,b,second,c,third,d,fourth




nicholas@mordor:~/regex$ 
nicholas@mordor:~/regex$ awk '{print $1 "\t\t" $3}' input.txt 
		
		
a		one
b		two
c		three
d		four
a		first
b		second
c		third
d		fourth
		
nicholas@mordor:~/regex$