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From: Josef Frank <josef DOT frank AT gmx DOT ch>
Subject: dd -- bs>=2G, error writing to /dev/null - possible bug? (win7; coreutils 8.26)
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Date: Sun, 12 Mar 2017 00:33:29 +0100
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Dear all,


dd utility has problems to write to /dev/null with bs>=2^31,
while bs<2^31 is ok.

Increasing bs further to 2^33 leads to extended error message

For description see below


jf




Steps to reproduce:


$ dd if=/dev/zero of=/dev/null bs=2147483647 count=1
1+0 records in
1+0 records out
2147483647 bytes (2.1 GB, 2.0 GiB) copied, 0.522774 s, 4.1 GB/s


$ dd if=/dev/zero of=/dev/null bs=2147483648 count=1
dd: error writing '/dev/null'
1+0 records in
0+0 records out
0 bytes copied, 0.517421 s, 0.0 kB/s


$ dd if=/dev/zero of=/dev/null bs=8589934591 count=1
dd: error writing '/dev/null'
1+0 records in
0+0 records out
0 bytes copied, 2.13474 s, 0.0 kB/s


$ dd if=/dev/zero of=/dev/null bs=8589934592 count=1
dd: error writing '/dev/null': No space left on device
1+0 records in
0+0 records out
0 bytes copied, 2.08004 s, 0.0 kB/s



In contrast the following lines (also coreutils 8.26) run fine (without
reporting any error):

head -c 2147483648 /dev/zero > /dev/null

head -c 8589934592 /dev/zero > /dev/null




Configuration:

Applies to several different machines with different amounts of main 
memory (up to 32GB, >24GB available), and sufficient free space on 
/var/tmp (100-180GB), all using Windows 7


$ uname -a
CYGWIN_NT-6.1 rab 2.7.0(0.306/5/3) 2017-02-12 13:18 x86_64 Cygwin


$ dd --version
dd (coreutils) 8.26
Packaged by Cygwin (8.26-2)
Copyright (C) 2016 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later
<http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Paul Rubin, David MacKenzie, and Stuart Kemp.


$ cygcheck dd
Found: C:\cygwin64\bin\dd.exe
Found: C:\cygwin64\bin\dd.exe
C:\cygwin64\bin\dd.exe
   C:\cygwin64\bin\cygwin1.dll
     C:\windows\system32\KERNEL32.dll
       C:\windows\system32\API-MS-Win-Core-RtlSupport-L1-1-0.dll
       C:\windows\system32\ntdll.dll
       C:\windows\system32\KERNELBASE.dll
       C:\windows\system32\API-MS-Win-Core-ProcessThreads-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Core-Heap-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Core-Memory-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Core-Handle-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Core-Synch-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Core-File-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Core-IO-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Core-ThreadPool-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Core-LibraryLoader-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Core-NamedPipe-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Core-Misc-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Core-SysInfo-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Core-Localization-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Core-ProcessEnvironment-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Core-String-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Core-Debug-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Core-ErrorHandling-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Core-Fibers-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Core-Util-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Core-Profile-L1-1-0.dll
       C:\windows\system32\API-MS-Win-Security-Base-L1-1-0.dll
   C:\cygwin64\bin\cygintl-8.dll
     C:\cygwin64\bin\cygiconv-2.dll

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