List specific files in command that expects `ls` piped into it

Question

I'm looking for an elegant cross-compatible way to direct the names of files into entr. I know the following works with Bash, but I'd like a command that would work in other shells.

(entr is a program that watches files and runs a command on start and when those files change. Its documentation shows ls *.ext, for example, piped into it - so it is expecting a newline separated list of legitimate filenames piped to it. It warns on bad filenames.)

multiliners

This command lets me list specific files with a multiline herestring:

$ entr echo "command ran" <<< "
> filename1
> filename2
> "

I find the quotation marks and having to list them on separate lines to be annoying. Also a quick search indicates it might not work in shells other than Bash.

I could use interactive cat:

$ cat | entr echo "command ran"
filename2
filename2

but again I have to do a newline each time, not much margin for error, and carefully enter Ctrl-D at the end.

A heredoc works similarly but involves bookend syntax.

$ cat << EOF | entr echo "command ran"
> filename1
> filename2
> EOF

one-liners:

I could also do ls, which looks nice at first glance:

$ ls filename1 filename2 | entr echo "command ran" 

But ls would strip out misspelled names, while entr validates and warns on improper names, and I'm worried about side-effects of calling ls in this way.

I could echo and pipe to tr before piping to entr:

$ echo filename1 filename2 | tr " " "\n" | entr echo "command ran"

But I don't like having all the extra commands.

The Question:

How do I write a short, elegant command that works in most (preferably all) shells? Syntax expected by posix would be ideal.

Answer 1

Since entr appears to want each file on a separate line you're pretty limited. You have to have each filename on a separate line. Any attempt to make it a single line (eg your tr example) will fail if the separator character is part of a filename ("this is a filename").

I'd just do the simple

echo 'filename 1
filename2' | entr echo "command ran"