Forcing the order of output fields from cut command

Question

I want to do something like this:

cat abcd.txt | cut -f 2,1 

and I want the order to be 2 and then 1 in the output. On the machine I am testing (FreeBSD 6), this is not happening (its printing in 1,2 order). Can you tell me how to do this?

I know I can always write a shell script to do this reversing, but I am looking for something using the 'cut' command options.

I think I am using version 5.2.1 of coreutils containing cut.

Solution 1

This can't be done using cut. According to the man page:

Selected input is written in the same order that it is read, and is written exactly once.

Patching cut has been proposed many times, but even complete patches have been rejected.

Instead, you can do it using awk, like this:

awk '{print($2,"\t",$1)}' abcd.txt

Replace the \t with whatever you're using as field separator.

Solution 2

Lars' answer was great but I found an even better one. The issue with his is it matches \t\t as no columns. To fix this use the following:

awk -v OFS="  " -F"\t" '{print $2, $1}' abcd.txt

Where:

-F"\t" is what to cut on exactly (tabs).

-v OFS=" " is what to seperate with (two spaces)

Example:

echo 'A\tB\t\tD' | awk -v OFS="    " -F"\t" '{print $2, $4, $1, $3}'

This outputs:

B    D    A    

Comments

[Panos Rontogiannis]

In Cygwin I had to replace -F"\t" with -F \t to make this work.

[internetdotcom]

Folks may be coming here confused because this (mis)behavior isn't documented in the cut man page found on *BSD/macOS. The man page references the POSIX.2 standard which does indeed specify the output order.