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Re: Bash scripting and large files: input with the read builtin from a r
From: |
Bob Proulx |
Subject: |
Re: Bash scripting and large files: input with the read builtin from a redirection gives unexpected result with files larger than 2GB. |
Date: |
Sun, 4 Mar 2012 13:05:42 -0700 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
Chet Ramey wrote:
> Jean-François Gagné wrote:
> > uname output: Linux xxxxxxxx 2.6.32-5-amd64 #1 SMP Tue Jun 14 09:42:28 UTC
> > 2011 x86_64 GNU/Linux
> > Machine Type: x86_64-pc-linux-gnu
>
> Compile and run the attached program. If it prints out `4', which it does
> on all of the Debian systems I've tried, file offsets are limited to 32
> bits, and accessing files greater than 2 GB is going to be unreliable.
Apparently all of the Debian systems you have tried are 32-bits
systems. On the reporter's 64-bit amd64 system it will print out 8.
Additionally the bash configure script includes the AC_SYS_LARGEFILE
macro which will test the ability of the system to use large files and
if the system is capable it will define _FILE_OFFSET_BITS=64 and in
that case the size off_t will be 8 bytes too. If you compile the test
program with -D_FILE_OFFSET_BITS=64 the result will also be 8 even on
32-bit systems.
By default the 32-bit bash will be large file aware on all systems
that support large files and will have been compiled with
_FILE_OFFSET_BITS=64. I just looked in the config.log from a build of
bash and it included these lines in the resulting config.log file.
configure:4710: checking for special C compiler options needed for large files
configure:4805: result: no
configure:4811: checking for _FILE_OFFSET_BITS value needed for large files
...
configure:4922: result: 64
...
ac_cv_sys_file_offset_bits=64
Bob
- Bash scripting and large files: input with the read builtin from a redirection gives unexpected result with files larger than 2GB., Jean-François Gagné, 2012/03/03
- Re: Bash scripting and large files: input with the read builtin from a redirection gives unexpected result with files larger than 2GB., Chet Ramey, 2012/03/04
- Re: Bash scripting and large files: input with the read builtin from a redirection gives unexpected result with files larger than 2GB., Jonathan Nieder, 2012/03/04
- Re: Bash scripting and large files: input with the read builtin from a redirection gives unexpected result with files larger than 2GB.,
Bob Proulx <=
- Re: Bash scripting and large files: input with the read builtin from a redirection gives unexpected result with files larger than 2GB., Andreas Schwab, 2012/03/04
- Re: Bash scripting and large files: input with the read builtin from a redirection gives unexpected result with files larger than 2GB., Chet Ramey, 2012/03/04
- Re: Bash scripting and large files: input with the read builtin from a redirection gives unexpected result with files larger than 2GB., Chet Ramey, 2012/03/04
- Re: Bash scripting and large files: input with the read builtin from a redirection gives unexpected result with files larger than 2GB., Andreas Schwab, 2012/03/04
- Re : Bash scripting and large files: input with the read builtin from a redirection gives unexpected result with files larger than 2GB., Jean-François Gagné, 2012/03/06
- Re : Bash scripting and large files: input with the read builtin from a redirection gives unexpected result with files larger than 2GB., Jean-François Gagné, 2012/03/08
Re: Bash scripting and large files: input with the read builtin from a redirection gives unexpected result with files larger than 2GB., Chet Ramey, 2012/03/04