bytevolc...@safe-mail.net wrote: > When I use ftruncate(2) to actually allocate the segment, the file is as > long as the segment that is allocated. > > Even if the file is unlinked before ftruncate(2) is called, enough free > space in the /tmp *file system* is required for the shared memory segment. > > Is using ftruncate(2) to lengthen the segment the right way to do it, or > is this yet another stupid limitation of POSIX shared memory?
ftruncate is really the only way to do it. There's nothing special about shm_open. It's just open with a different name. If you want the files on a different filesystem, you can use open.
