How can I `cat` files with a number of fixed lines before/between/after?

Question

I am looking for a bash one-liner which can cat a number of files with a number of fixed lines.

file1.txt:

file1 line 1
file1 line 2

file2.txt

file2 line 1
file2 line 2

Then I am looking for something like

cat-with-strings foo file1.txt bar file2.txt baz

producing output

foo
file1 line 1
file1 line 2
bar
file2 line 1
file2 line 2
baz

How can I do this in a single line of bash, using standard linux tools (sed, awk, cat, etc) and without creating any files to hold foo, bar, or baz?

Answer 1

Typing on my phone so apologies for a sketch, untested answer.

Surely you can just concatinate (cat) everything as if everything was a file:

cat <( echo foo ) file1.txt <( echo bar ) file2.txt <( echo baz )

Answer 2

sh -c 'while [ $# -gt 0 ] ; do echo "$1" ; cat "${2:-/dev/null}" ; shift 2 2>/dev/null; done' - foo file1 bar file2 baz

In general requiring this to be a 1-liner is pretty silly, who cares if it is one line if you put it in a shell function or file?

Answer 3

With one command using any awk in any shell on every Unix box

$ awk 'FNR==1{print x} 1; END{print x}' x='foo' file1 x='bar' file2 x='baz'
foo
file1 line 1
file1 line 2
bar
file2 line 1
file2 line 2
baz