Redirection of stdin and stdout can break stdin

[andry81]

Note

Windows XP x64 only issue.

Warning

You must restart console on each test, otherwise it won't reproduce.

There is exist the check command on stdin reopen:

https://github.com/andry81/contools/tree/HEAD/scripts/tools/std/is_stdin_reopen.bat

Test:

"%SystemRoot%\System32\timeout.exe" /T 0 >nul 2>&1 && echo OK || echo NOT OK
"%SystemRoot%\System32\timeout.exe" /T 0 >nul 2>&1 && echo OK || echo NOT OK
"%SystemRoot%\System32\timeout.exe" /T 0 >nul 2>&1 && echo OK || echo NOT OK

Result:

OK
OK
OK

If try to reopen stdin and stdout, then the command inverts the result.

Test:

"%SystemRoot%\System32\timeout.exe" /T 0 >nul 2>&1 && echo OK || echo NOT OK
call; >nul <nul
"%SystemRoot%\System32\timeout.exe" /T 0 >nul 2>&1 && echo OK || echo NOT OK
call; >nul <nul
"%SystemRoot%\System32\timeout.exe" /T 0 >nul 2>&1 && echo OK || echo NOT OK
call; >nul <nul
"%SystemRoot%\System32\timeout.exe" /T 0 >nul 2>&1 && echo OK || echo NOT OK

Result:

OK
NOT OK
OK
NOT OK

Note that the timeout.exe call itself with the inner redirection breaks the stdin. Not the call; >nul <nul itself.

Test:

call; >nul <nul
"%SystemRoot%\System32\timeout.exe" /T 0 >nul 2>&1 && echo OK || echo NOT OK
call; >nul <nul
"%SystemRoot%\System32\timeout.exe" /T 0 >nul 2>&1 && echo OK || echo NOT OK
call; >nul <nul
"%SystemRoot%\System32\timeout.exe" /T 0 >nul 2>&1 && echo OK || echo NOT OK

Result:

OK
OK
OK

Test:

call; >nul <nul
"%SystemRoot%\System32\timeout.exe" /T 0 && echo OK || echo NOT OK
call; >nul <nul
"%SystemRoot%\System32\timeout.exe" /T 0 && echo OK || echo NOT OK
call; >nul <nul
"%SystemRoot%\System32\timeout.exe" /T 0 && echo OK || echo NOT OK

Result:

Waiting for 0 seconds, press a key to continue ...
OK
ERROR: Input redirection is not supported, exiting the process immediately.
NOT OK

Waiting for 0 seconds, press a key to continue ...
OK

Note

The reopen order in call; >nul <nul command affects the result.

Note

The call; >nul 2>nul does not affect anything nor the order of redirection.