The tail utility is part of the coreutils on linux. Source tarball: ftp://ftp.gnu.org/gnu/coreutils/coreutils-7.4.tar.gz Source file: https://git.savannah.gnu.org/cgit/coreutils.git/tree/src/tail.c (original http link) I’ve always found FreeBSD to have far clearer source code than the gnu utilities. So here’s tail.c in the FreeBSD project: http://svnweb.freebsd.org/csrg/usr.bin/tail/tail.c?view=markup
You don’t see anything, because of buffering. The output is shown, when there are enough lines or end of file is reached. tail -f means wait for more input, but there are no more lines in file and so the pipe to grep is never closed. If you omit -f from tail the output is … Read more
I might be mistaken, but your function doesn’t need to be tail recursive in this case. Tail recursion helps us to not consume the stack in case we use recursive functions. In your case, however, we are not actually consuming the stack in the way a typical recursive function would. This is because the “recursive” … Read more
Use tail’s –pid option and tail will stop when the shell dies. No need to add extra to the tailed file. sh -c ‘tail -n +0 –pid=$$ -f /tmp/foo | { sed “/EOF/ q” && kill $$ ;}’
Under Python 3.x, you can do this nicely: >>> head, *tail = [1, 1, 2, 3, 5, 8, 13, 21, 34, 55] >>> head 1 >>> tail [1, 2, 3, 5, 8, 13, 21, 34, 55] A new feature in 3.x is to use the * operator in unpacking, to mean any extra values. It … Read more
I believe the problem here is that the first grep is buffering the output which means the second grep won’t see it until the buffer is flushed. Try adding the –line-buffered option on your first grep: tail -f access_log | grep –line-buffered “127.0.0.1” | grep -v “.css” For more info, see “BashFAQ/009 — What is … Read more
Use the -wait parameter with Get-Content, which displays lines as they are added to the file. This feature was present in PowerShell v1, but for some reason not documented well in v2. Here is an example Get-Content -Path “C:\scripts\test.txt” -Wait Once you run this, update and save the file and you will see the changes … Read more
Well, the simplest way would be to constantly read from the file, check what’s new and test for hits. import time def watch(fn, words): fp = open(fn, ‘r’) while True: new = fp.readline() # Once all lines are read this just returns ” # until the file changes and a new line appears if new: … Read more
If you use PowerShell then this works: Get-Content filenamehere -Wait -Tail 30 Posting Stefan’s comment from below, so people don’t miss it PowerShell 3 introduces a -Tail parameter to include only the last x lines
Take a look at Apache Commons implementation of Tailer class. It does seem to handle log rotation as well.