Contents
What is a open file table?
The Open File Table stores the information about all the files that are open while the OS is running. If the file is opened again by some other process (or the same process), the Open system call a new entry is created in the open file table.
Is open file table per-process?
The Per-Process Open File Table in the PCB of each process stores information about files opened by the corresponding process. Each entry in the Per-Process Open File Table has the index to the file’s entry in the System-wide Open File Table.
Which data structure is used in the kernel to represent an open file?
system open-file table
So the kernel keeps a data structure called the system open-file table which has an entry for each connection.
What is kernel structure?
The kernel data structures are very important as they store data about the current state of the system. For example, if a new process is created in the system, a kernel data structure is created that contains the details about the process. They may contain data as well as pointers to other data structures.
Which is the Open File Table in the operating system?
A system-wide open file table, containing a copy of the FCB for every currently open file in the system, as well as some other related information. A per-process open file table, containing a pointer to the system open file table as well as some other information.
Is the vnode table the same as the Open File Table?
Several file descriptors may actually refer to the same system open-file table entries. That entry in the system open-file table can’t be removed until all of those referencing file descriptors have been closed. Several system open-file table entries may actually refer to the same vnode table entry.
How does the file table work in Unix?
So there is neither just one file table entry for an open file nor is there just one per process there is one per open () call, and it is shared if the file descriptor is dup () ed or fork () ed. When two or more processes open a file for reading, there’s an entry in the open file table per open.
Is the file table in the filesystem or in memory?
The open file table is kept per process and contains references into the in-memory inode table as well as pointers to buffers, and state information (like fseek (2) value and flags from open (2).