More Filters
Paste

The "paste" Filter

We have used grep, cut, and colrm to substract content. Now let's learn to add.

The paste command is used to put two files together. The format for paste is:
     paste file1 file2 ...

Instead of putting file1 on top of file2, file1 and file2 are combined side-by-side.

For example, combining file1 and file2, we would get:
file1

1111
2222
3333
4444

file2

AAAA
BBBB
CCCC
DDDD

paste file1 file2

1111	AAAA
2222	BBBB
3333	CCCC
4444	DDDD
By default, paste inserts a tab between the two columns (which is kinda convenient since cut likes to use tabs also).

Assignment

Create a new script named "swap" that will swap the colomns in a two column file. The two columns should be seperated by a tab.

To test your script you will need to create your own dummy data file with two columns that you can test swapping back and forth.

Here is an example run: 
> cat testdata.txt
aaa     bbb
aaaaa   bbbbb
aaaaaaa bbbbbbb

> swap testdata.txt

> cat testdata.txt
bbb     aaa
bbbbb   aaaaa
bbbbbbb aaaaaaa

> swap testdata.txt

> cat testdata.txt
aaa     bbb
aaaaa   bbbbb
aaaaaaa bbbbbbb

This assignment will be kinda tricky. For example, you have to figure out where to keep the first and second columns until you are ready to recombine them.

Note that your script should have NO side-effects.