[apps/cli] Support reading from stdin #249

[LuoZijun]

Resolve #249

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This change is 

[behnam]

Thanks for working on this, @LuoZijun!

Reviewable status: 0 of 2 files reviewed, 1 unresolved discussion (waiting on @LuoZijun)

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apps/cli/src/bin/unic-echo.rs, line 151 at r1 (raw file):

        let done_clone = done.clone();

        let handler = thread::spawn(move ||{

Could you elaborate on why using a separate thread to read from stdin here?

AFAIU, we should be able to do the same thing with non-blocking IO without spawning a thread. Or, if we want to go with blocking IO, still going with direct read in the main thread seems to be reasonable for such a small CLI tool.

What do you think?

[LuoZijun]

@behnam

If we support accepting parameters from the basic input,
the main thread will still blocked when this $ ./unic-echo appears.

Of course, if everyone thinks this is not going to bother the user,
the block style approach will be very straightforward.
and i am happy to change to a synchronous way.

Use case:

• ./unic-echo "STRING ..."
• cat hello.txt | ./unic-echo or ./unic-echo < hello.txt
• ./unic-echo

[behnam]

Oh, I think I see what you mean.

I think blocking reading from stdin should only happen if we explicitly want to read from stdin.

One common condition for reading from stdin is when there are no (non-optional) arguments passed to the CLI. (Like unix's echo without any file-names passed to it.)

Another common option is when the argument is one HYPHEN-MINUS ("-"). In this case, the position of the HYPHEN-MINUS can tell us if the stdin text should be placed before or after any other regular argument.

If none of them applies (there's at least one argument passed to the CLI and none of the is "-") the stdin is not even (blocking) opened.

So, all of these cases would result in "Hello world" string to be echoed/inspected:

• unic-echo "Hello world" and
  unic-inspect "Hello world"

• echo "Hello world" | unic-echo and
  echo "Hello world" | unic-inspect

• echo "Hello world" | unic-echo - and
  echo "Hello world" | unic-inspect -

• echo "ignored" | unic-echo "Hello world" and
  echo "ignored" | unic-inspect "Hello world"

• echo "world" | unic-echo "Hello " - and
  echo "world" | unic-inspect "Hello " -

What do you think?

[LuoZijun]

@behnam

I think that's great.

BTW: Actually is --, not - :)

[LuoZijun]

@behnam ping ?