Why do I get 'Bad file descriptor' when trying sys.stdin.read() in subversion pre-revprop-change py script?

问题

I'm trying pre-revprop-change hook script on a Windows machine, but find a tough problem.

I distill my problem to the following scenario:

I have C:\csvn\data\repositories\tr1\hooks\pre-revprop-change.bat with content:

D:\svntest\testhook.py %*
exit %ERRORLEVEL%

testhook.py is:

import os, sys

if __name__ == '__main__':
    # sys.stderr.write(sys.version+'\n') # this is OK, tried.
    newtext = sys.stdin.read() # try to read new log message

    sys.stderr.write('newtext is: %s\n'%newtext)

    exit(2)

However, when doing a client-side svn propset svn:log --revprop -r 2 "newtext" , I got python error:

Traceback (most recent call last):
  File "D:\svntest\testhook.py", line 5, in <module>
    newtext = sys.stdin.read() # try to read new log message
IOError: [Errno 9] Bad file descriptor

What's the cause of this error?

It seems that pre-revprop-change.bat does not pass STDIN handle to the py script. Yes, I verified that pre-revprop-change.bat can fetch text from STDIN(according to instructions in Read stdin stream in a batch file).

I also tried to run pre-revprop-change.bat directly from command line, sys.stdin.read() is OK.

Please kindly help me out.

Screen shot below:

Env:

Windows Server 2003
Collabnet Subversion Edge 2.3(svn 1.7.3 and Apache 2.2.22)
Install Python 2.7.1 msi from python.org

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I'm sorry to say: I should have written in the .bat

exit %ERRORLEVEL%

instead of

exit /b %ERRORLEVEL%

For someone who have tried it with me, please fix it and try again. The /b seems to have pre-revprop-change.bat always exit with 0. TIP: Without /b, running the .bat directly from a cmd window will cause the cmd window to close, so we'd better try it with cmd /c "pre-revprop-change.bat some param".

Quick way to reproduce this problem below

What's more, for those who is still interested, please

download this file package http://down.nlscan.com/misc/chjsvnpyhook.zip ,
extract them to D:\ ,
cd into D:\svntest\tr1_local ,
run elog.bat (svn propset svn:log --revprop -r 2 "newtext")

then my problem will be reproduced. (Requirement: svn.exe 1.7 command line(whether collabnet or TortoiseSVN), and Python 2.7 installed)

If you still cannot reproduce the error. I've prepared a VMware virtual machine that exhibits the problem exactly. Download the VM at http://down.nlscan.com/misc/chj/winxp-svnhook-py-stdin-error.7z (link expected to be valid until Sep 2013). VMware Player 3.0(free) is sufficient to run that VM.

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Very nice workaround provided by @nmenezes, with c:\Python27\python.exe D:\svntest\testhook.py %* in bat .

回答1:

SVN is executing the script without an associated console. So you won't see anything displayed on STDOUT. Everything sent to STDERR is displayed as a message on SVN, if the script returns an error code different of 0.

This kind of script should run unattended, it is independent of input or output from the user.

You can try to pass the property value as an extra command line parameter. To do so, change your .bat to:

@echo off
set /p NEWTEXT=
test.py %* %NEWTEXT%
exit /b %ERRORLEVEL%

And the .py to:

import os, sys

if __name__ == '__main__':   
    newtext = sys.argv[6]
    sys.stderr.write('newtext is: %s\n'% newtext)
    exit(2)

I read the batch STDIN to NEWTEXT variable and I pass it to your script as an extra command line parameter.

This solution does not work for multiple lines values. So, I tried again your original solutions and it worked fine.

svn propset svn:log --revprop -r 3 -F svn.txt

In this case, the property value is read from the svn.txt file, a text file with multiple lines. In this case, the option with set /p does not work, as we discussed in the comments. But the original script works.

For information, 5 properties are passed on the command line:

1 - repository

2 - revision number

3 - user

4 - property name

5 - operation (M in this case)

The property value is passed on the stdin of the batch script.

@Chen, I finally downloaded the image. The problem is solved when you change the hook batch to:

c:\python27\python.exe d:\svntest\testhook.py %*
exit %ERRORLEVEL%

It looks that the way your XP machine executes python directly is misconfigured.

回答2:

Isn't it up to your batch file to direct the stdin it received into the script that it calls?

For reference: http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/redirection.mspx?mfr=true

Maybe you can just prefix the call to your script with the > symbol to have this happen?

> D:\svntest\testhook.py %*
exit /b %ERRORLEVEL%

It seems like if the batch file can read from stdin, then SVN is doing what it is supposed to and it is up to your batch file to make that available to the additional script that you call.

来源：https://stackoverflow.com/questions/12453354/why-do-i-get-bad-file-descriptor-when-trying-sys-stdin-read-in-subversion-pr

标签

python

svn

svn-hooks