standards: Mmap

1 
1 5.11 Mmap
1 =========
1 
1 If you use 'mmap' to read or write files, don't assume it either works
1 on all files or fails for all files.  It may work on some files and fail
1 on others.
1 
1    The proper way to use 'mmap' is to try it on the specific file for
1 which you want to use it--and if 'mmap' doesn't work, fall back on doing
1 the job in another way using 'read' and 'write'.
1 
1    The reason this precaution is needed is that the GNU kernel (the
1 HURD) provides a user-extensible file system, in which there can be many
1 different kinds of "ordinary files".  Many of them support 'mmap', but
1 some do not.  It is important to make programs handle all these kinds of
1 files.
1