shared memory segment, shmat() ...

[Joseph Yip]

A few days ago, I came across some code that uses shmat() and related
functions. The program maps a file using shmat() (we are using IBM RT,
running AIX 2.2.1). Basically, the program opens an binary digital image
file and maps it. Can someone explain to me what is shared memory
segment and how to use it? In /usr/include/sys/shm.h (AIX), SHM_MAP flag
maps a file instead of share segment. But in SunOS 4.0, shm.h does not
have this flag. How can I map a file in this case?

Thank you.

- Joseph Yip
Email: joseph at zeus.ee.utexas.edu