mem(7)
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mem Special File
main system memory
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DESCRIPTION
Mem is a character special pseudo-device that provides access to
the system's physical main memory for direct reading and writing.
The file pointer is treated as a physical byte address within
main memory.
For the open and close system calls, user visible functionality
is the same as for an ordinary disk file.
For the read system call, the contents of physical main memory at
the address contained in the file pointer are transferred into
the caller's buffer. If any part of the requested data would be
past the end of physical memory, no data is transferred and the
error ENXIO is returned. No consistency guarantees are made; the
physical memory being read may change while the read is in
progress.
For the write system call, the contents of caller's buffer are
transferred into physical main memory at the address contained in
the file pointer. If the write call would attempt to transfer
data to locations past the end of physical main memory, no data
will be transferred and the error ENXIO will be returned.
Correct operation of the system is not guaranteed after physical
memory has been modified with this call.
There are no ioctl system calls specific to the character special
device mem. Other ioctl calls that apply to ordinary disk files
also apply to mem.
Select always returns READY for both read and write operations.
FILES
/dev/mem
SEE ALSO
kmem(7)
DG/UX 4.00 Page 1
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