How to implement a horizontal cat?

Question

Standard cat concatenates files line by line (row by row, if you will). I find myself needing a horizontal cat command more and more often recently; i.e. a command that takes a list of files and concatenates them horizontally, column by column. So far I’ve used ad-hoc workarounds but I’d like to know if there exists a good solution for this.

To clarify, consider the following comparison between cat and hcat of two files:

$ cat a.dat 1.dat
a b
c d
1 2
3 4
$ hcat -s ' ' a.dat 1.dat
a b 1 2
c d 3 4

(Unlike for cat we need to specify a separator since by convention UNIX files don’t have a column separator at the end.)

Answer 1

This sounds like a job for paste:

paste -d ' ' a.dat 1.dat

Output:

a b 1 2
c d 3 4