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I would like to run two programs simultaneously from a batch file, and redirect the first program's output into a text file like:

start python arg1 arg2 > out.txt
start 2nd.exe %1 arg2 arg3

While the programs run as expected, all output is shown on stdout.

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This ought to work. Without knowing anything, I wonder if is doing something funny with output. – zpletan Sep 21 '11 at 17:17
No, but it writes to stderr. – none Sep 21 '11 at 17:25
That's why—> only redirects stdout (I think). In any case, it looks like you already have what you need. – zpletan Sep 21 '11 at 20:51
up vote 14 down vote accepted

You might need to do it this way:

start cmd /c python arg1 arg2 ^> out.txt
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Thank you, but it does not work for me (out.txt is not even created in the local directory) – none Sep 21 '11 at 17:52
I tested it with CScript and a VBscript, so the idea is sound. Are you doing something "extra" in your command line that's not listed here, like double quotes? – Patrick S. Sep 21 '11 at 18:19
Sorry, something went awfully wrong - it works! – none Sep 21 '11 at 18:27

Redirection is applied to the start command, but somehow not to the cmd.exe instance it runs.

If the > operator is escaped, everything should work:

start arg1 arg2 ^> out.txt

(If you want to redirect stderr as well, use 2^> for it.)

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Thank you, but it does not work for me. – none Sep 21 '11 at 17:52

Additionally, if you want to redirect both stderr and stdout this works for me

start call delay.bat ^1^> log.txt ^2^>^&^1

It seems every character basically needs to be escaped. This command normally looks like this:

delay.bat 1> log.txt 2>&1

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What did the trick for me was moving the command into a separate batch file:

rem this first batch file triggers the second one:
start the_second.bat arg1 arg2 out.txt

the_second.bat then looks like this:

python %1 %2 > %3
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This is a very inelegant workaround compared to the correct answer. – DavidPostill 2 days ago
The "correct answer" didn't work for me with a similiar problem and I thought it might be a solution people at least might want to know about. – Florian Straub yesterday
I have to disagree. Learning the correct way to escape characters in command is a much better idea. – DavidPostill yesterday
Please teach me how to escape attaching output using >>. – Florian Straub yesterday
I already told you. Read the accepted answer. – DavidPostill yesterday

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