python - Why is mmap returning a size of zero? -

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i'm working on beaglebone (running angstrom linux) , trying use python's mmap module gain read , write access /dev/mem file.

however, reason, code below prints value of zero. i'm new mmap , i'm not sure if there obvious missing.

from mmap import mmap  mmap_offset=0x44c00000 mmap_size=0x48ffffff-mmap_offset  open("/dev/mem", "r+b") f:     testmap=mmap(f.fileno(),mmap_size,offset=mmap_offset)  print testmap.size() print testmap[0]

returns:

0 8

because device inodes /dev/mem report apparent size of 0 when queried stat(). how special device nodes implemented, it's not useful ask device node how large is. (consider /dev/zero, /dev/kbd, /dev/urandom, , device node used communication , not data storage, such device nodes representing photo scanners or input devices.)

you should still able retrieve data mmap handle.


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