Linux – Why does less tail mode stop working

lesslinuxshell

Using the less command on linux in tail mode (F command or less -f) consistently stops working on certain machines and/or certain files. New changes simply stop showing up.

I know I've fixed this before, long ago, but I don't recall what the solution was.

Any ideas?

Best Answer

Try using less --follow-name. Even if the file has the same name, the process(es) updating it may be doing so in a way which changes the file's inode -- so from the OS point of view, it's a new file after the updates.

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You can write a bash script to scan all the file descriptors listed in /proc (assume you have that) and list/kill the processes.

/proc/$m/fd/$n is the n-th file descriptor for PID m presented as a symbolic link. busybox does have readlink support, so you should be able to automatic it.

Edit: Just to say this is essentially re-implementing lsof, but it's actually fairly simple.

Linux – Filter tail command through multiple grep commands to separate files

It might be easier if you use more than one line to do this. You could write a bash script:

#!/bin/bash

tail -f test.log | while read line; do
    if echo "$line" | grep -q "Error"; then
        echo "$line" >> error.log
    elif echo "$line" | grep -q "Warning"; then
        echo "$line" >> warning.log
    # The following is in case you want to print out lines that do not match 
    else
        echo "$line"
    fi
done

Best Answer

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