Solution

File operations

• File exists to store information and allow it to be retrieved later.

• Different system provides different operations to allow storage and retrieval.

• The most common system calls are shown below.

• Create :

  The purpose of the call is to announce that the file is coming and to set some attributes.

• Delete:

  When the file is no longer needed, it has to be deleted to free up disk space.

• Open:

  The purpose of the open call is to allow the system to fetch the attributes.

• Close:

  When all accesses are finished, the attributes and disk addresses are no longer needed, so the file should be closed to free up table space.

• Read:

  Data are read from file. Usually the bytes come from the current position.

• Write:

  Data are written to the file, usually at the current position.

• Append:

  This call is restricted form of write. It can only add data to the end of file.

• Seek:

  For a random access files, a method is needed to specify from where to take the data. Seek repositions the file pointer to a specific place in the file.

• Get attributes:

  Processes often need to read the file attributes to do their work.

• Set attributes:

  Some of the attributes are user settable and can be changed after the file has been created. This system call makes that possible.

• Rename:

  It frequently happens that a user needs to change the name of an existing file. This system call makes it possible.