[SOLVED] redirecting output

[Two-eyes]

Hi, I've been browsing and searching for this for 1/2 an hour or so, but I still don't get it.
I have this batch file but isn't working.  From what I found, it should be correct, but.....

Here's the code:

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@echo off

echo hiya 1>doesntexist\blabla.txt 2>error.txt

When I run is from command prompt:

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c:\> test.bat
The system cannot find the path specified

Shouldn't the error message be written in error.txt?  Or did I understand wrong?

Thanks for any help

Two-eyes

[macdad-]

CMD always displays the errors in batch files, whenever it hits an error, it terminates the batch file

[billrich]

Two Eyes wrote:

<<"Here's the code:

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@echo off

 ">>

Test the redirect at command prompt.


C:\>cd  doesntexist

C:\doesntexist>dir
 Volume in drive C has no label.
 Volume Serial Number is F4A3-D6B3

 Directory of C:\doesntexist

09/11/2009  07:23 PM    <DIR>          .
09/11/2009  07:23 PM    <DIR>          ..
09/11/2009  07:23 PM                 7 blabla.txt
               1 File(s)              7 bytes
               2 Dir(s)  306,860,113,920 bytes free

C:\doesntexist>type blabla.txt
hiya

C:\doesntexist>

[Two-eyes]

@macdad-: ...should there have been a fullstop/period between "errors" and in batch files".  If that's the case, I understand.  Is there a work around or a way to continue the batch file? I believe I can evaluate %errorlevel%, i.e.

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IF %errorlevel% NEQ 0 ECHO error %errorlevel% occurred>error.txt
But how do I get the actual message?

@billrich: the directory "doesnt exist" does not exist, ergo the name.  So it should output the error "the system couldnt find path specified".  But I want to capture that error message, and print it in error.txt.

Thanks Two-eyes

[Salmon Trout]

@macdad-: ...should there have been a fullstop/period between "errors" and in batch files".  If that's the case, I understand. 

CMD always displays the errors in batch files, whenever it hits an error, it terminates the batch file

No; the sentence makes perfect sense as it stands. The first clause states that CMD always displays the errors caused when batch files are run. The second and third, which are linked, state that when it [cmd.exe] encounters an error, [any error] the batch file is terminated. Perhaps I would have put a semicolon after 'files', but to make that a criticism would be excessively picky in my opinion.

[T.C.]

CMD always displays the errors in batch files, whenever it hits an error, it terminates the batch file

That's incorrect and a very dangerous assumption.  In lots of cases CMD issues the error message and continues with the next command.  Try this:

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@echo off
cls

pushd doesntexist\

dir /a-d

The directory listing is produced for the default directory not the directory which was intended in the Pushd command.  If, instead of dir, the command had been del all sorts of brown stuff might occur.  With commands like Pushd and CD IMHO it's always best to use e.g.:

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Pushd doesntexist\ || echo Error: Pushd failed - job terminated. && exit/b

[Salmon Trout]

test.bat:

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@echo off
echo hiya > doesntexist\blabla.txt
(1)
Console:

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S:\>test.bat
The system cannot find the path specified.
S:\>
(2)
Console:

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S:\>test.bat > err.txt
The system cannot find the path specified.
S:\>
err.txt:

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(3)
Console:

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S:\>test.bat 2> err.txt
S:\>
err.txt:

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The system cannot find the path specified.


[Two-eyes]

@ Salmon Trout: aaaaaaah, I see.  You put one redirection in the batch file, and the other in the console.  That solves it.

Just a quick question: was my syntax wrong, i.e. I can't put two redirections in a line.  Cos I can do

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something > myfile.txt 2>&1
and that's two redirections, unless I'm not understanding this well.

Thanks
Two-eyes

[Salmon Trout]

I think the answer is that the 2> and  &1 notation is for programs & scripts that write error messages to stderr and console messages to stdout, so that we may combine stderr and stdout into one stream, but not for cmd.exe internal commands. An error in one of these stops the show so you have to do it the way I showed.

 

[Two-eyes]

is the simplest way I can think of putting it

Thanks....I'm new to this

When you say chain, do you mean
 1) it won't continue reading the current line ">myfile.txt 2>&1"
or
 2) it won't continue reading the next lines of code(if this were a batch file)

T-E

[Salmon Trout]

1) it won't continue reading the current line ">myfile.txt 2>&1"

[Two-eyes]

But if it won't read that line, how will it send the error message to myfile.txt.  Or will it jump to the "2>"?

I also re-ask the question: can i put two redirections in a line of command?

Sorry, but I am like this.  I always want to know what the compiler/executer is doing.   It's just my fascination how simple electric pulses do such complicated things

Thanks

[Salmon Trout]

Code: [Select]

(echo hello > \notexistdir\file.txt) 2>error.txt
This works. You have to break the line into blocks using brackets.

This forces cmd.exe to process the echo statement first.

[Two-eyes]

ahaaaaa.
Got it
Thanks

[Salmon Trout]

Break the line. See edited post above.

Alternative: (note alternative placements of redirection)

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2>error.txt (echo hello > \nodir\nofile.txt)
also note these formats for redirecting multiple lines

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(
echo line 1
echo line 2
echo line 3
) > output.txt

Or...

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> output.txt (
echo line 1
echo line 2
echo line 3
)

or for 1 line

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> output.txt echo Hello!