How to cat files in linux vertically?

Question

I have n files containing one line and want to concatenate them:

Input files:

file_1
A B C

file_2 
1 2 3 

Desired console ouput result:

A B C
1 2 3 

But with:

$ cat file_1 file_2 

I get:

A B C1 2 3 

Answer 1

Try

echo | cat file_1 - file_2

Alternatively, terminate the last line of file_1 with a new-line symbol.

Yet another way:

$ echo > n
$ cat file_1 n file_2 n file_1 n file_2 n
A B C
1 2 3
A B C
1 2 3

Answer 2

If you have more than 2 files, you can use a loop with the shell and use echo to insert a new line:

for f in file1 file2 file3; do cat "$f"; echo; done > output

Answer 3

If you only have two files, you could use echo to output a new line and put that between your two files like so:

echo | cat file1 - file2

Answer 4

Here is what i observe using bash shell on Ubuntu 12.04.

$ echo "1 2 3" > file1
$ echo "a b c" > file2
$ cat file1 file2
1 2 3
a b c

Separate distinct lines.

It looks like echo command ensures that proper terminated strings are written to both the files.

Answer 5

Your file1 is missing a newline at the end. So when you cat them, there's no newline printed to separate file1 from file2.

You either need to modify file1 to include a trailing newline or insert it in some other way.