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How to tail a log file in Linux?
Basically, you’d define a function to be called on, say, signal 17, then put a sub-script in the background that will send that signal at some later time: Then if you reach 1200 seconds, your function is called and you can choose what to do (like signal your tail/grep combo that is watching for your pattern in order to kill it)
How to use tail-F in a shell script?
I am writing a shell script that is supposed to monitor some log files and redirect the output to a file. I am using tail -f command to do so, but it doesnt seem to work.
Which is the best way to follow a log file?
For multiple possibilities, you could maybe drop the grep and instead use a case within the while. The capital -F tells tail to watch for the log file to be rotated; i.e. if the current file gets renamed and another file with the same name takes its place, tail will switch over to the new file.
How to start and end tail in Bash?
Put a timeout on the read, tail -f logfile | read -t 30 line Start tail with –pid=$$, that way it’ll exit when the bash-process has finished. It’ll cover all cases I can think of (server hangs with no output, server exits, server starts correctly).
How does tail run from its own sub-shell?
By making tail run from it’s own sub-shell, we can place it in the background so it runs independently.
How to decouple the termination of tail from grep?
All you really need is to decouple the termination of tail from grep. That way, once grep ends, the script can continue even if tail hasn’t ended yet. So this simple method will get you there: grep will block until it has found the string, whereupon it will exit.
Is there a way to tail a file?
The accepted answer doesn’t work and will never exit (because althouth read -t exits, the prior pipe commands ( tail -f | grep) will only be notified of read -t exit when they try to write to output, which never happens until the string matches). A one-liner is probably feasible, but here are scripted (working) approaches.