Why redirection sometimes fails ?

[Ed Dyreen]

Code: Select all

@echo off &ver

echo.this redirection fails
reg.EXE add "" /f 2>&1>nul
echo.this redirection succeeds
reg.EXE add "" /f 2>nul>nul

pause
exit

Code: Select all

Microsoft Windows XP [versie 5.1.2600]
this redirection fails

Fout: ongeldige sleutelnaam
this redirection succeeds
Druk op een toets om door te gaan. . .

[foxidrive]

echo.this redirection fails
reg.EXE add "" /f 2>&1>nul

This could be confusing the parser as 1>nul is redirecting STDOUT to nul.

I think the order of redirection matters: IE if you do not explicitly set STDOUT >nul before setting 2>&1 then STDERR is going to be redirected to where STDOUT was going at the time, in this case to the console.

So 1>nul 2>&1 is the order to use, or EG:

reg.EXE add "" /f >nul 2>&1

[Ed Dyreen]

Code: Select all

echo.this redirection succeeds
reg.EXE add "" /f>nul 2>&1

I hadn't thought of that, sweet

Thank u foxi !

[Squashman]

Code: Select all

echo.this redirection succeeds
reg.EXE add "" /f>nul 2>&1

I hadn't thought of that, sweet

Thank u foxi !

You just saw me doing that in another thread.
viewtopic.php?f=3&t=3708&p=19590#p19590

[Ed Dyreen]

'
No I didn't

I know DOS rearranges commands before it executes them.

Code: Select all

@echo on &prompt $G &ver

reg.EXE add "">nul 2>&1
>nul 2>&1reg.EXE add ""

reg.EXE add "" 2>&1>nul
2>&1>nul reg.EXE add ""

pause
exit

But I didn't realize switching the order would.

Code: Select all

Microsoft Windows XP [versie 5.1.2600]

> reg.EXE add "" 1>nul 2>&1

> reg.EXE add "" 1>nul 2>&1

> reg.EXE add ""  2>&1 1>nul

Fout: ongeldige sleutelnaam

> reg.EXE add "" 2>&1 1>nul

Fout: ongeldige sleutelnaam

> pause
Druk op een toets om door te gaan. . .

To be honest, I've examined my codes and apparently I've been doing it "right" often enough. It's only recently that I discovered why it's important to document why you do something the way you do it. As if you don't you'll forget. Seems I'm not an elephant after all. I've documented it and should be fine now