A possible solution is the Unix command line utility 'cut'. For example, if file fred.txt is

1 2 3 4 5 6 7
1 2 3
1 2 3 4 5

Then the command

cut -f 1,3,5,7,9 -d ' ' fred.txt

produces (to stdout) the results

1 3 5 7
1 3
1 3 5

That's the odd numbered columns, separated by the space ' ' character (up to column #9). By putting in at least as many column indexes after the '-f' option as there are actual columns, you can pick out what you want. You can use the AFNI 'count' utility for this purpose, as in

cut -d ' ' -f `count -dig 1 -comma 1 99 2` fred.txt

Here, the backquote operator `count ...` means "run the command inside the backquotes, capture the stdout and put it on the command line here". If you try the given count command by itself, you get

count -dig 1 -comma 1 99 2
1,3,5,7,9,11,13,15,17,19,21,23,25,27,29,31,33,35,37,39,41,43,45,47,49,51,53,55,57,59,61,63,65,67,69,71,73,75,77,79,81,83,85,87,89,91,93,95,97,99

For the even columns, use 'count -dig 1 -comma 2 100 2' instead. Note that the option -d ' ' is needed since the default separator for 'cut' is the tab character, so if you used spaces, then each line is considered to be one big column and you won't like the results. Obviously, you need to test the results to make sure they work with your files!