[Tcl-bugs] [ tcl-Bugs-1245953 ] exec ">>" does "a"-style opening, not "APPEND"

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Bugs item #1245953, was opened at 2005-07-27 13:12
Message generated for change (Comment added) made by dkf
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Category: 25. Channel System
Group: current: 8.5a3
>Status: Closed
>Resolution: Fixed
Priority: 9
Submitted By: Andreas Leitgeb (avl42)
>Assigned to: Donal K. Fellows (dkf)
Summary: exec ">>" does "a"-style opening, not "APPEND"

Initial Comment:
when I do:
  exec myprog >> logfile
this happens:

   open("logfile", O_WRONLY|O_CREAT|O_LARGEFILE, 0666) = 5
   _llseek(5, 0, [0], SEEK_END)            = 0

This is just a bad thing. Everyone used to shell-syntax 
expects the file to be opened with the "O_APPEND" flag,
such that two concurrent processes outputting to the
same file will not overwrite each others output, but always
append.


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>Comment By: Donal K. Fellows (dkf)
Date: 2005-07-28 16:30

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Fixed in HEAD and 8.4 branch; test is a little fragile on
very heavily loaded systems, but I don't know of any better
way to test it easily.

Note that Windows is not fixed, and cannot be fixed due to
fundamental lamenesses in the Win32 API (i.e. no equivalent
flag on file handles is available). Blame Microsoft.

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Comment By: Donal K. Fellows (dkf)
Date: 2005-07-27 13:24

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O_APPEND looks universally available (or at least we already
use it without having configure check for it) so absolutely
no reason to not use it at all.

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Comment By: Donal K. Fellows (dkf)
Date: 2005-07-27 13:18

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If O_APPEND is available (can we count on it?) we SHOULD use it.

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