Questions tagged [tail]

Watching updates at the end of a file, with or without the tail utility

Filter by
Sorted by
Tagged with
5
votes
2answers
5k views

Send EOF to named pipe - cleaning up / drying up fifo

If I have some random processes reading from a named pipe: tail -f MYNAMEDPIPED cat MYNAMEDPIPE | someOtherProc Elsewhere, I have a handle on MYNAMEDPIPED by name. is there a safe and clean way to ...
5
votes
2answers
6k views

Tail -f piped through grep not outputing to file, but outputs to console

I'm using the following command tail -f /mydir/myfile | grep "searchterm" >> outfile Without the -f it works fine, but with the -f, which I need, nothing is written to the file. The following ...
4
votes
2answers
583 views

Why xargs can't work with tail -f?

I want tail -f /var/log/syslog | grep it with pattern "arpwatch" and send every line to myself via jabber: xmpp username@jabber.server using xargs tail -f /var/log/syslog | grep arpwatch | xargs ...
3
votes
5answers
2k views

Only output most recent 10 (or n) lines of a lengthy command output

I have a command that outputs thousands of lines. I actually need these lines in order to see the progress of the command. But I do not need to see more than the 10 most recent lines. How can I do ...
3
votes
1answer
791 views

POSIX head and tail not feature equivalent

The documentation for POSIX tail's -n option says that The origin for counting shall be 1; that is, -n +1 represents the first line of the file, -n -1 the last. So tail -n 10 (used later on the ...
2
votes
2answers
810 views

How to cat named pipe without waiting

If there is nothing in a named pipe and I do: cat my_named_pipe it will wait until data arrives. Is there a flag I can use to exit immediately if there is no data to be read? Or perhaps a command ...
12
votes
2answers
2k views

How to start tailing a file that has not been yet created

I use tail to monitor the progress of jobs that I know will write their progress to disk. Almost always, I know which file they will create before they start running (the jobs are dispatched by a ...
4
votes
0answers
349 views

Combing head and tail in a single call via pipe [duplicate]

On a regular basis, I am piping the output of some program to either head or tail. Now, suppose that I want to see the first AND last 10 lines of piped output, such that I could do something like ./...
3
votes
1answer
177 views

Why are some file changes not shown in tail -f?

I tried to follow the mysql history file with: tail -f ~/.mysql_history in another window I entered as the same user: mysql -u someotheruser -p and none of the following commands are shown in my ...
3
votes
2answers
4k views

Using tail to follow daily log file in Bash

I have a task to use a bash script to monitor a couple of log files named with the current day, eg. YYYY-MM-DD.log. (1) I used tail -f to follow the file but unable to deal file rotation. Even if ...
2
votes
1answer
8k views

how do i redirect output from tailf & grep to a file [duplicate]

All I wanted is to grep for specific lines in an ongoing log and re-direct it to some file.. tailf log | grep "some words" Now, I want the above command output to get re-directed to some file in on-...
1
vote
0answers
174 views

Why does GNU head/tail read the whole file? [duplicate]

I have a huge file and want to see its beginning and end. However, when I use head and tail, it apparently tries to read the whole file. Since the file is larger than a terabyte, this takes a very ...
0
votes
1answer
49 views

Too many emails sent when sending emails when specific URL has been visited in Apache Logs

In this question, a solution was found to automatically send an email each time a specific URL is visited (such as ?src=foo), as seen in the Apache logs: tail -F -n0 /var/log/apache2/...
0
votes
1answer
5k views

How to tail dmesg on CentOS 7

In a CentOS 7 server, I typed dmesg and noted the time stamp of the last entry. Next, I typed tail -f /var/log/dmesg in a DIFFERENT TERMINAL ON THE SAME MACHINE, so that I could watch the log tail. ...

1
2