How do I force close a file in Linux?
open /dev/null with O_WRONLY, then dup2 to close the offending file descriptor and reuse it’s descriptor for /dev/null. This way any reads or writes to the file descriptor will fail. If you dup a descriptor to /dev/null , any writes will not fail, but succeed, and the reads will succeed and return 0 (eof).
Why do you need to close file descriptors?
close() closes a file descriptor, so that it no longer refers to any file and may be reused. Any record locks (see fcntl(2)) held on the file it was associated with, and owned by the process, are removed (regardless of the file descriptor that was used to obtain the lock).
What happens if you don’t close descriptor?
As long as your program is running, if you keep opening files without closing them, the most likely result is that you will run out of file descriptors/handles available for your process, and attempting to open more files will fail eventually.
Is there a way to unmount a file system?
You can use the umount-foption to forcibly unmount a file system that is busy in an emergency situation. This practice is not recommended under normal circumstances because the unmounting of a file system with open files could cause a loss of data. This option is only available for UFS and NFS file systems.
Which is the correct way to close a file descriptor?
In that aspect, close is a bit like free: it is invalidating the value (file descriptor for close, pointer for free) passed to it. When possible, you could set the file descriptor to -1 (or some other invalid value) after a successful close (2), so code close (fd); fd = -1; for example.
What happens when you mount a file system?
Mounting a file system attaches that file system to a directory ( mount point) and makes it available to the system. The root ( /) file system is always mounted. Any other file system can be connected or disconnected from the root ( / ) file system. When you mount a file system,…
How to force close a file descriptor in gdb?
In the gdb case the descriptor (or also FILE * handle) would need to be checked whether it is read-only or read-write or write-only and an appropriate replacement opened on /dev/null. If not, a once read-only handle that is now write-only will cause needless errors should the process attempt to read from that. What Could Go Wrong?