Ending tail -f after print n lines
I have the following.
- A Java process writing logs on file
- A shell script starting the Java process.
I need to read the log file after start Java process to check correct starting.
I have try with tail -f but it remain append forever. I need tail stop after print n lines. There is a way like -n option for previuos lines?
You can pipe the output of tail -f to head to limit the amount of lines shown:
tail -f [PATH] | head -n 100
to only show 100 lines in total.
New lines only
With the plain tail -f, the first 10 lines are from the file as it already exists:
tail -f file.log | head -30
writes 10 lines of log.txt when it is run, and 20 (n-10) lines that are added later.
With a log file, you normally use -f (--follow) to see the lines written in the future.
To see only the 30 lines that where written after tail was started,
limit the initial output to 0:
tail -f -n0 file.log | head -30