I think that the question is:
Should appending to a non-existent UNICODE file automatically write the FFFE?
From: Mcdaniel, Daryl [mailto:daryl.mcdan...@intel.com]
Sent: Tuesday, July 29, 2014 4:08 PM
To: edk2-devel@lists.sourceforge.net
Subject: Re: [edk2] Bug in EFI Shell V2.0
Regarding appending from Uefi Shell 2.0, it is behaving as written:
echo 1234 > test.dat # Writes 14 bytes to file "test.dat": L"1234\r\n"
prefixed with the Unicode Byte Ordering Mark <BOM> (0xFFFE).
del test.dat
echo 1234 >> test.dat # Writes 12 bytes to file "test.dat": L"1234\r\n" with
NO prefix.
echo 5678 >> test.dat # Attempts to append 12 bytes to the Unicode file
"test.dat".
# Fails because "test.dat" is NOT Unicode, No UBOC prefix
echo 6789 >>a test.dat # Appends 6 ASCII bytes to test.dat. Success, but
first line is UCS2 and second is ASCII.
Thus, the echo command is failing because you are attempting to append Unicode
text to what appears to be an ASCII file. The Shell is trying to protect you
from error.
Some would think that redirection should identify a request to append to an
empty or non-existent file and go ahead and prepend the BOM. That isn't the
case here.
I am unable to reproduce the Python error. Here is a transcript of what I did.
HD15a1:\Efi\StdLib\tmp\> ver
UEFI Interactive Shell v2.0
Copyright 2009-2013 Intel(r) Corporation. All rights reserved.
UEFI v2.31 (EDK II, 0x00010000)
HD15a1:\Efi\StdLib\tmp\> rm baz.txt
Deleting 'HD15a1:\Efi\StdLib\tmp\baz.txt'
Delete successful
HD15a1:\Efi\StdLib\tmp\> echo "Now is the time" >> baz.txt
HD15a1:\Efi\StdLib\tmp\> echo "Rainbow pony" >>a baz.txt
HD15a1:\Efi\StdLib\tmp\> echo "Born Free" >>a baz.txt
HD15a1:\Efi\StdLib\tmp\> type baz.txt
..o.w. .i.s. .t.h.e. .t.i.m.e.
.Rainbow Pony
Born Free
HD15a1:\Efi\StdLib\tmp\> Python
Python 2.7.2 (default, Jul 23 2014, 15:04:28) [C] on uefi
Type "help", "copyright", "credits" or "license" for more information.
>>> f = open('baz.txt', 'a')
>>> f.write('Zanzibar\n')
>>> f.close()
>>> r = open('baz.txt', 'r')
>>> r.readline()
'N\x00o\x00w\x00 \x00i\x00s\x00 \x00t\x00h\x00e\x00
\x00t\x00i\x00m\x00e\x00\r\x00\n'
>>> r.readline()
'\x00Rainbow Pony\r\n'
>>> r.readline()
'Born Free\r\n'
>>> r.readline()
'Zanzibar\n'
>>> r.close()
>>> exit()
HD15a1:\Efi\StdLib\tmp\>
I get identical results using a version of Python built in 2012.
Daryl McDaniel
"It is the mark of an educated mind to be able to entertain a thought without
accepting it."
- Aristotle
From: lowell_den...@dell.com<mailto:lowell_den...@dell.com>
[mailto:lowell_den...@dell.com]
Sent: Tuesday, July 29, 2014 11:18 AM
To: edk2-devel@lists.sourceforge.net<mailto:edk2-devel@lists.sourceforge.net>
Subject: [edk2] Bug in EFI Shell V2.0
Every copy of EFI Shell V2.0 that I have found seems to have a file processing
bug.
It looks like appending to a file does not work as expected. The following
shell snippet does not work:
del test.dat
echo 1234 >> test.dat # This works
echo 5678 >> test.dat # This give "Error.
Unable to redirect file"
If I modify that shell snippet as follows it works:
del test.dat
echo 1234 > test.dat
echo 5678 >> test.dat
Additionally appending as ASCII also works:
del test.dat
echo 1234 >>a test.dat
echo 5678 >>a test.dat
This error carries over to programming interfaces. If I try to open an
existing file for append in Python I get an error"
f = open('ExistingFile', 'a')
# ERROR
However, if I open the file in mode 'r+' there is no error:
f = open('ExistingFile', 'r+')
f.seek(0,2)
What is going on here?
Thanks,
Lowell Dennis
Platform Software Engineer
Dell | Business Client
office +1 512 723 8880
fax +1 512 283 0149
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