What is file locking?
File locking is a mechanism used to secure the integrity of files being shared between users. This allows different people to commit changes to files without causing conflicts when multiple parties are attempting to make changes.
File locking allows only one user or process to access a file and make changes at any given time. This eliminates the problem of interceding updates.
Interceding updates can cause delays in workflows and can damage files when file locking is not implemented to prevent these issues. The following is an example have an interceding update situation:
People A and B are working together on a project. This requires them both to make changes to the same document. If person A opens the file and is currently making edits, then person B attempts to open the file, it will appear to them as a completely empty document. It may also interrupt person A’s session and delete any unsaved changes they made to the file. This is the conflict.
With file locking in place, when person A opens a file to make edits and person B attempts to open the file simultaneously, person B will be unable to open it. Instead, they will receive the message – “file being accessed by some other candidate.” This prevents the interceding update issue, maintaining a steady workflow and avoiding any damage to files.
Types of file locking
There are multiple types of file locking that can be implemented depending on how a file will be used. These are exclusive or shared locking.
Exclusive locking is used when a file will be edited by a group of people who are all granted the same level of permissions. In this case, only one person can access the file and make changes at a time.
Shared locks are used when people only need to read files, not edit them. The shared lock prevents anyone from making changes, but users can all view the file simultaneously.
Flock() vs. lockf()
- The lockf() command is used to lock individual parts of a file.
- The flock() command locks entire files at once.