Print two files in two columns side-by-side

Question

I want to output two text files in two columns — one on the left side and other one on the right.

paste doesn't solve the problem, because it only insert a character as delimiter, so if the first file has lines of different lengths output will be twisted:

$ cat file1
looooooooong line
line
$ cat file2
hello
world
$ paste file1 file2
looooooooong line   hello
line    world

If there was a command to add trailing spaces like fmt --add-spaces --width 50 the problem would be solved⁽¹⁾:

$ paste <(fmt --add-spaces --width 50 file1) file2
looooooooong line                                 hello
line                                              world

But I don't know a simple way to do this.

So how to merge files horizontally and print them to standard output without twisting?

In fact I just want to read them side-by-side.

---

^{(1) UPD: command to add trailing spaces does exist, e. g. xargs -d '\n' printf '%-50s\n'. But running
$ paste <(add-trailing-spaces file1) file2 won't produce expected visual output when file1 has fewer lines than file2.}

Answer 1

With single pr command:

pr -Tm file[12]

• -T (--omit-pagination) - omit page headers and trailers, eliminate any pagination by form feeds set in input files

• -m (--merge) - print all files in parallel, one in each column

Answer 2

What about paste file{1,2}| column -s $'\t' -tn?

looooooooong line line  hello
line                    world

• This is telling column to use Tab as columns' separator where we takes it from the paste command which is the default seperator there if not specified; generally:

  paste -d'X' file{1,2}| column -s $'X' -tn

  where X means any single character. You need to choose the one which granted that won't be occur in your files.

• The -t option is used to determine the number of columns the input contains.

• This will not add long tab between two files while other answers does.

• this will work even if there was empty line(s) in file1 and it will not print second file in print area of file1, see below input/ouput

  Input file1:

  looooooooong line
  
  line
  

  Input file2:

  hello
  world
  

  Output:

  looooooooong line  hello
                     world
  line
  

Answer 3

A portable solution:

$ paste file1 file2 | awk -F'\t' '{ printf("%-30s %s\n", $1, $2) }'
looooooooong line              hello
line                           world

This uses paste to produce a tab-delimited input for awk.

The awk script simply takes the two tab-delimited fields and outputs them using printf(). A column of 30 characters is reserved for the first file. The %-30s means "30 positions of string data with left alignment". Removing the - would produce a column aligned to the right, and changing 30 would change the column width.

It also deals with uneven length files. Here I've added lines to the second file:

looooooooong line              hello
line                           world
                               hello
                               world
                               hello
                               world

And, when reversing the order of the files on the command line:

hello                          looooooooong line
world                          line
hello
world
hello
world

Answer 4

Try:

paste -d '\n' file1 file2 | xargs -d '\n' printf '%-30s  %-30s\n'

Inspired by @Kusalananda's solution.

^{Note: The -d parameter of xargs is only available on GNU version, but not on BSD.}