Reformat every other line with paste

Sometimes a very simple command can accomplish amazing tasks.

Recently I had a list with alternating entries on every other line with about 200 lines, and lots of uneven text. But  I wanted to have 2 columns instead.

A quick online search let me find a new way of using a familiar command called paste that I had used before. It is amazing what a simple dash - can do!

Dash - represents output, in the case below 2 dashes will mean alternate lines.

This is much easier with an example. Consider the list of data with alternating name and numbers contained in file s.txt:

Jo:
1543
Meg:
685
Beth:
465
Amy:
645

In a Text-Based Terminal (Mac/Linux) I can send the content of the file to the paste utility and add 2 dashes and get 2 columns.

paste - - < s.txt 
Jo: 1543
Meg:    685
Beth:   465
Amy:    645

Using 4 dashes would yield l reorganize in 4 columns, 6 dashes in 6 columns…

paste - - - - < s.txt 
Jo: 1543    Meg:    685
Beth:   465 Amy:    645

While this is nice, the separation of the 2 columns is by blank spaces. To get tab-delimited data there is an example at the end of the manual pages specifying delimiters tab  (\t) and newline (\n)

paste -s -d '\t\n' - < s.txt 
Jo:     1543
Meg:    685
Beth:   465
Amy:    645

Now, imagine that the file has 2000 lines… that would not be so exciting to do this by hand! And what is there are a few dozens of such files…

See paste manual pages for more.