Originally Posted by unSpawn
If /dev/shm is accessable you can use that to write to. Otherwise no you can't, only if your unprivileged user has been granted root rights (CAP_SYS_ADMIN in this case).
Thank you very much for this answer.
I wrote a perl-program which does a lot of file-access, reading a line, parsing the line, several x-thausand times. total runtime was 5 hours.
I then copied everything to /dev/shm in the hope that this would speed things up. it didn't, runtime is exactly the same as from HD!
So I guess the parsing of the line takes much more time than I thought, or /dev/shm got swapped or whatever.