What happens to a process when the filesystem is full

Question

What happens to a process if the filesystem is full? Does the kernel send us a signal to shutdown and if so what signal is it. Obviously, a program will probably crash if it writes to the file system but I'm curious as to how this occurs (in gory kernel/operating system detail).

Answer 1

What happens to a process if the filesystem fills up?

Operations that would require additional disk space on the full partition (like creating or appending to a file) fail with an errno of ENOSPC .

No signal is sent, as a full filesystem is not a critical condition which makes a signal necessary. It's a routine, easily handled error.

Answer 2

There is no reason a program should crash when the filesystem is full. Obviously file writes will fail, but a well-written program should be able to cope with that - in C, this would mean that fopen returns NULL or ferror returns a non-zero value, etc. I have encountered this many times, and some nasty things can happen such as overwriting a file with a blank version, but never a program crash. If it does happen, it is presumably because the author of the program tried to use a NULL file descriptor or some similar problem, in which case the program would receive a SIGSEGV as usual.