Question

I would like to output a file’s contents appended with a string without creating a new line.

so far my command places the appended string on a new line:

sed -e 'a foo' file.txt
>> file contents...
>> foo

I want the output to look like this:

>> file contents...foo

Answer 1

With sed (tested successfully on Archlinux & Minix):

sed '$s/$/foo/' file.txt

$ at the beginning, mean end of file.

If you need to add foo on each lines :

sed 's/$/foo/' file.txt

In the latest context, $ mean end of line