Question

This is for a Unix class:

1. Explain the difference between soft link and hard link and come out with your own step-by-step example demonstrating the differences between two link types.

2. What’s the final effect of the following statements? (hint: Explain them in terms of the stdio and kernel buffers.)

fflush(aFilePointer);

fsync(fileno(aFilePointer));

Answer 1

Difference between softlink and hardlinks:

• Hardlink means an additional name is given to the existing file whereas a softlink is something like a shortcut, it will point to the original file.
• The inode number of a hardlink will be same as that of the original file, whereas inode number of software is different.
• Hardlink will be there if we delete the original file, whereas in softlink, the pointer will move to a dangling position, when the original file is deleted.

Hardlink command:

ln source_file dest_file

Softlink commmand

ln -s source_file dest_file

2. fflush usually works on file level, and it will flush the internal buffer of the file. Whereas fsync works at a lower level as compared to fflush, because it will instruct the OS to flush the nuffer to physical media. Usually fsync work as file descriptor.