Is there a command/program for OS X that allows me to hook to a file and display its changes in realtime without re-opening it, much like "top" monitors system processes in realtime?


You can use tail to monitor single log file.

If file is deleted, then created again you may want to use tail -F to actively monitor file changes

If same file is being appended too use tail -f to actively monitor file changes

  • 1
    It doesn't seem to display changes as the file updates – Mark F Feb 6 '11 at 18:38
  • It does, at least on FreeBSD and linuxes. Should work on Mac OS X too. – gelraen Feb 6 '11 at 18:41
  • @Mark how do you modify the file during checking? – ulidtko Feb 6 '11 at 18:48
  • Perhaps it has something to do with the fact that the file is in a Dropbox and is updated perhaps a bit differently? – Mark F Feb 6 '11 at 18:48
  • 2
    Try tail -F. Consult with man tail for more details about these options. – gelraen Feb 6 '11 at 18:51

Another alternative may be doing less the-interesting-file and hitting Shift+F.


If you are doing this on file sync'd by dropbox the chances are it is creating a new file with a different inode so the tail -f command and the less +F command do not work since they are still referencing the old file handle they opened initially.

I suggest trying

watch "tail /path/to/filename"

It feels hackish but at least every X seconds it will re run tail on the filename giving you the updated output regardless of whether or not the inodes change on the file.

protected by Falcon Momot Nov 17 '14 at 9:43

Thank you for your interest in this question. Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site (the association bonus does not count).

Would you like to answer one of these unanswered questions instead?

Not the answer you're looking for? Browse other questions tagged or ask your own question.