CODEWITHSUNDEEP
bashawk
markos.aivazoglou
markos.aivazoglou

Reputation: 174

Print result to every second line of output file in awk

Seems no one yet stumbled upon my problem,so here it goes.
So sets say,i want to take the third column $3 of every other line 2nd,4th,6th etc of input file(i know how to do that) and then print the result at the exactly same position in an output file.
I mean,$3 of 2nd line of input,to $3 of 2nd line of output and goes on.

I want this,using awk from bash.

Upvotes: 0

Views: 595

Answers (2)

Jotne
Jotne

Reputation: 41446

Here is how to do it with awk

awk 'FNR==NR {a[NR]=$3;next} FNR%2==0 {$3=a[FNR]}1' firstfile secondfile

This will take data from firstfile and update secondfile using column $3 and every second line.
Data is replaced in the same position.

cat firstfile
1 one green
2 two red
3 three blue
4 four orange
5 five yellow
6 six brown


cat secondfile
1 one jan
2 two feb
3 three mars
4 four april
5 five jun
6 six juli

Running awk command:

1 one jan
2 two red
3 three mars
4 four orange
5 five jun
6 six brown

Too store data back to secondfile

awk 'FNR==NR {a[NR]=$3;next} FNR%2==0 {$3=a[FNR]}1' firstfile secondfile > tmp && mv tmp secondfile

Upvotes: 2

Mark Setchell
Mark Setchell

Reputation: 207405

It seems you can't explain what you want very well, so I'll guess and maybe you can say what is wrong and it will get solved by process of elimination...

Given an input file called file, like this:

Line 0,field2,field3,90
Line 1,field2,field3,80
Line 2,field2,field3,82
Line 3,field2,field3,21 
Line 4,field2,field3,85

The following awk will print every other line's field3 in the same place as it found it, but without the other stuff around it:

awk -F, 'NR%2{print ",,"$3"\n,,";}' file

Output:

,,field3
,,
,,field3
,,
,,field3
,,

Upvotes: 1

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