tail -f not tracking file changes

Question

I was recently looking into using tail -f to monitor some text files like so: tail -f /var/sometext.

However, when I did some testing, it doesn't seem to work. What I did was I created a new file and ran: tail -f /home/name/text Then, I opened the log in vim and did some editing, saved it, and it seems that tail is not "seeing" the change.

The weird thing is, running echo "hello" >> /home/name/text seems to work fine (tail sees the change). I read somewhere this has something to do with file descriptors and new inodes being created when saving a file.

Can someone explain this for me? I didn't quite get how this actually works, but I have an idea what file descriptors are though.

Solution

-f follows by inode. If you want to follow by name, such as when a program completely recreates the file, then use -F instead.

Comments

[Lyle]

Neat, I never knew that. It pays to read the manpages of utilities even(especially?) if you use them all the time!

[pabouk - Ukraine stay strong]

The tail -f command operates on a file (file descriptor after opening the file). Although in fact the fresh modifications of the file are still in the memory (buffers, cache) it does not matter. tail still accesses the file through the file descriptor. It does not matter how the file is modified. --- The answer by Ignacio Vazquez-Abrams is correct - the editor does not modify the current file (which is opened in tail), it saves the changes to a new file with the same name as the old one.