stat: Adds support to read a filename redirected to stdin

[crazystylus]

Explanation:

touch f && stat - < f creates an empty file and stat after seeing - tries to find the file which is being redirected to stdin and prints details for that file.

Solution:

On detecting -, canonicalize /dev/stdin which will point to the file which is being redirected to stdin

NOTE stat doesn't read the content of the file, and this can be verified

Fixes #3241

[sylvestre]

Could you please add a test to make sure we don't regress?
thanks

[crazystylus]

Hi,
It's not possible to add test cases for this at the moment because when I attach a file handle to process's stdin for redirection in std::process::Command or UCommand, rust will instead attach a pipe. std::fs::canonicalize is failing to resolve /dev/stdin when it points to a linux pipe at the moment.

Reference: rust-lang/rust#95239

[jfinkels]

Even though there is no simple way to test this, I checked out this branch and tested on my machine and it seemed to work as expected. 👍

[sylvestre]

Thanks!

[jhscheer]

Hi, It's not possible to add test cases for this at the moment because when I attach a file handle to process's stdin for redirection in std::process::Command or UCommand, rust will instead attach a pipe. std::fs::canonicalize is failing to resolve /dev/stdin when it points to a linux pipe at the moment.

Reference: rust-lang/rust#95239

It was a bit tricky, but it can be tested like this:

coreutils/tests/by-util/test_stat.rs

Lines 353 to 367 in 122c7d6

	// $ touch f && stat - < f
	// File: -
	// Size: 0 Blocks: 0 IO Block: 4096 regular empty file
	let ts = TestScenario::new(util_name!());
	let at = &ts.fixtures;
	at.touch("f");
	new_ucmd!()
	.arg("-")
	.set_stdin(std::fs::File::open("f").unwrap())
	.run()
	.no_stderr()
	.stdout_contains("regular empty file")
	.stdout_contains("File: -")
	.succeeded();