How can I view periodic updates/appends to a file? (ex: growing log file)
tail -f will show you the growing log file. On some systems (e.g. OpenBSD), this will automatically track a rotated log file to the new file with the same name (which is usually what you want). To get the equivalent functionality on GNU systems, use tail -F instead.
This is helpful if you need to view only the updates to the file after your last view.
# Start by setting n=1 tail -n $n testfile; n="+$(( $(wc -l < testfile) + 1 ))"
Every invocation of this gives the update to the file from where we stopped last. If you know the line number from where you want to start, set n to that.