Does mmap need shm_open?

Question

I have a situation where I need to perform file IO but I'm sandboxed. So, I'm using shm_open with mmap, to return a file descriptor which I can happily read/write to/from in memory.

The problem I have is that a platform that I am porting to does not have shm_open. Does mmap require arg 5 to be a "file descriptor"? Or is there some other way I can use mmap without shm_open?

Thanks!

Answer 1

You can use the MAP_ANONYMOUS flag to just map a piece of memory. This is basically the same as calling malloc, and no data you write will be saved as it's all in memory.