Swap two columns - awk, sed, python, perl

Question

I've got data in a large file (280 columns wide, 7 million lines long!) and I need to swap the first two columns. I think I could do this with some kind of awk for loop, to print $2, $1, then a range to the end of the file - but I don't know how to do the range part, and I can't print $2, $1, $3...$280! Most of the column swap answers I've seen here are specific to small files with a manageable number of columns, so I need something that doesn't depend on specifying every column number.

The file is tab delimited:

Affy-id chr 0 pos NA06984 NA06985 NA06986 NA06989 

Answer 1

You can do this by swapping values of the first two fields:

awk ' { t = $1; $1 = $2; $2 = t; print; } ' input_file 

Answer 2

I tried the answer of perreal with cygwin on a windows system with a tab separated file. It didn't work, because the standard separator is space.

If you encounter the same problem, try this instead:

awk -F $'\t' ' { t = $1; $1 = $2; $2 = t; print; } ' OFS=$'\t' input_file 

Incoming separator is defined by -F $'\t' and the seperator for output by OFS=$'\t'.

awk -F $'\t' ' { t = $1; $1 = $2; $2 = t; print; } ' OFS=$'\t' input_file > output_file