How can I adjust a text file in VIM to have two columns instead of three while not splitting paired data? - awk

Question

Hello there and thank you for reading this!
I have a very large text file that looks something like this:
a1 b1 a2
b2 a3 b3
a4 b4 a5
b5 a6 b6
I would like my text file to look like this:
a1 b1
a2 b2
a3 b3
a4 b4
a5 b5
a6 b6
In reality, these values are paired lon/lat coordinates. If it is useful the values look like:
1.591336e+02 4.978998e+01 1.591162e+02
4.977995e+01 1.590988e+02 4.976991e+01
1.590815e+02 4.975988e+01 1.590641e+02
4.974984e+01 1.590468e+02 4.973980e+01
I have been learning in vim, but I do have access to other tools if this is easier done elsewhere. Should I be looking for a sed or awk command that will assess the amount of spaces in a given row? I appreciate any and all advice, and if I can offer any more information, I would be glad to!
I have searched for other folks who have had this question, but I don't know how to apply some of the solutions I've seen for similar problems to this - and I'm afraid of messing up this very large file. I am expecting the answer to be something using sed or awk, but I don't know how to be successful with these commands with what I've found so far. I'm rather new to coding and this site, so if I missed this question already being asked, I apologize!
All the best!
EDIT: I used
sed 's/\s/\n/2;P;D' file.txt > newfile.txt
to turn my file into:
a1 b1
a2^M
b2 a3
b3^M
a4 b4
a5^M
b5 a6
b6^M
I then used:
dos2unix newfile.txt
to get rid of the ^M within the data. I haven't made it to the structure, but I am one step closer.

Answer 1

$ tr ' ' '\n' <input_file|paste -d" " - -
a1 b1
a2 b2
a3 b3
$ sed 's/ /\n/2; P; D' <(tr '\n' ' ' <input_file)
a1 b1
a2 b2
a3 b3
$ tr '\n' ' ' <input_file|xargs -d" " printf '%s %s\n'
a1 b1
a2 b2
a3 b3

Answer 2

An approach using awk
% awk '{for(i=1;i<=NF;i++){x++; printf x%2==0 ? $i"\n" : $i" "}}' file
a1 b1
a2 b2
a3 b3
a4 b4
a5 b5
a6 b6
Data
% cat file
a1 b1 a2
b2 a3 b3
a4 b4 a5
b5 a6 b6

Answer 3

Using GNU sed
$ sed -Ez 's/([^ \n]*)[ \n]([^ \n]* ?)\n?/\1 \2\n/g' input_file
a1 b1
a2 b2
a3 b3
a4 b4
a5 b5
a6 b6

Answer 4

Using cut:
$ cut -d' ' -f1,2 test
a1 b1
b2 a3
a4 b4
b5 a6

Answer 5

In vim you can
:%j
to join all the lines, then
:s/\([^ ]\+ [^ ]\+\) /\1\r/g
to turn every 2nd space into a newline.
With perl
perl -0777 -lpe 's/(\S+)\s+(\S+)\s+/$1 $2\n/g' file
That reads the whole file into memory, so it depends on what "very large" is. Is it smaller than the amount of memory you have?

Answer 6

FWIW, here is a bit of a meta-answer.
Vim lets you filter all or some of the lines in your buffer via an external program with :help :!. It is very handy because, wile Vim can do a lot, there are plenty of use cases for which external tools would do a better job.
So… if you already have the file opened in Vim, you should be able to apply the provided answers with little effort:
:%!tr ' ' '\n' | paste -d" " - -
:%!tr '\n' ' ' | sed 's/ /\n/2; P; D'
:%!perl -0777 -lpe 's/(\S+)\s+(\S+)\s+/$1 $2\n/g'
etc.
Of note:
The command after the [range]! takes the lines covered by [range] as standard input which makes constructs like <filename unnecessary in this context.
Vim expands % to the current filename and # to the alternate filename if they exist so they usually need to be escaped, as in:
:%!tr '\n' ' ' | xargs printf '\%s \%s\n'
There's a lot to learn from this thread. Good luck.

Answer 7

This might work for you (GNU sed):
sed '$!N;y/\n/ /;s/ /\n/2;P;D' file
Append the following line if not the last.
Translate all newlines to spaces.
Replace the second space by a newline.
Print the first line, delete the first line and repeat.