UNIX for Dummies Questions & Answers

Hi,

I was trying to change the value of the 4th column (put '1' in the 4th column of each row). My awk command is:

awk -F, '{$3=1;}1' OFS= input.txt > ./test_out.txt

My input file is:

Code:

a 1 2 31
b 4 5 61
c 7 8 91

My output file (test_out.txt)is:

Code:

a 1 2 31
b 4 5 61
c 7 8 91

What I actually want is:

Code:

a 1 2 1
b 4 5 1
c 7 8 1

What do I need to change in my awk code?

thanks!!

Moderator's Comments:

As noted many times before, please use CODE tags for sample input and output as well as for code sample.

The field you are trying to change is number 4th

Code:

awk '{$4=1}1' input.txt > test_out.txt

There is no need to change the Field Separator to a comma (-F,) or the Output Field Separator (OFS= )

It looks like Aia may have already solved your problem, but I'm a little confused...

With the sample input given above, the code shown above would produce the output:

Code:

a 1 2 311
b 4 5 611
c 7 8 911

instead of what you showed us above.

And, it isn't just that you don't "need" to change FS and OFS; setting FS to comma (when your input field separator is a space and there are no commas in your input) means that each of your input lines contains one field instead of four. And setting OFS to an empty string removes all of your specified input field separators when you set any specific field.

You can do it with just replacing the 4th column

awk '{print $1,$2,$3,"1"}' input.txt > output.txt

Since the field being changed is being set to a non-zero numeric string (and also works if it is being set to a non-empty, non-numeric string), the simplest way to do it is:

Code:

awk '$4=1' input.txt > output.txt