Linux Commands Examples

A great documentation place for Linux commands

tail

output the last part of files

Synopsis

tail [OPTION]... [FILE]...


add an example, a script, a trick and tips

: email address (won't be displayed)
: name

Step 2

Thanks for this example ! - It will be moderated and published shortly.

Feel free to post other examples
Oops ! There is a tiny cockup. A damn 404 cockup. Please contact the loosy team who maintains and develops this wonderful site by clicking in the mighty feedback button on the side of the page. Say what happened. Thanks!

examples

1
source

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

0
tail -f `ls -t | head -1`



##What does it do ?

I open the latest file is always, and see data that are added on the fly. It is useful to see what is happening in a log file, in a log directory for example.



##Ouput:

The last lines of the last modified file, and lines that are added from then.

(won't work if the latest one is a directory)
example added by yoshimura
0
source

How to easily break up a text file into pieces smaller than a threshold?

There already is a nice tool for that: split

> man 1 split 

NAME
     split -- split a file into pieces

SYNOPSIS
     split [-l line_count] [-a suffix_length] [file [prefix]]
     split -b byte_count[K|k|M|m|G|g] [-a suffix_length] [file [prefix]]
     split -p pattern [-a suffix_length] [file [prefix]]


split --bytes 50M test.out test.out_ would split the file test.out into test.out_xaa, test.out_xab, test.out_xac, ...

A much uglier solution would be to use dd

dd if=test.out of=test.out.part1 bs=1M count=50 skip=0 creates a file named test.out.part1 with the first 50M from test.out. You can increase the value for skip to 1 to get the second chunk, to 2 for the third etc etc. Just make sure to also change the filenames or you will end up overwriting the same output file.

0
source

Combine tail -f with grep?

You almost wrote the answer, which is :

tail -f file.log | grep "foobar"

That's it.

0
source

How to grab a random section in the middle of a huge file?

You just have to write a little program to seek to some random spot and read some amount of lines.

An example in Python (reads one line, but you can modify it):

def get_random_line():
    """Return a randomly selected line from a file."""
    import random
    fo = open("/some/file.txt")
    try:
        point = random.randrange(fo.size)
        fo.seek(point)
        c = fo.read(1)
        while c != '\n' and fo.tell() > 0:
            fo.seek(-2, 1)
            c = fo.read(1)
        line = fo.readline().strip()
    finally:
        fo.close()
    return line

0
source

tail -f not tracking file changes

-f follows by inode. If you want to follow by name, such as when a program completely recreates the file, then use -F instead.

0
source

Linux application to tail multiple log files (like OS X Console.app)

Not sure about other distros, but Ubuntu has/had the GNOME System Log Viewer.

0
source

quick tail on a huge file on linux

Apart from splitting up the file into some smaller files, you could simply open the file and seek it to something you may think of as close to the end of the file.

After that, you read as much lines as there may come, and, if you reach EOF without all of your 10000000 desired lines, you just need to make a diff from the first position you guessed, and a new -- prior -- position, and try to read the n = diff lines.

I do not actually know if tail does so, or if there's any available POSIX tool that performs this kind of operation; implementing this shouldn't take more than five minutes, I guess (: This may be of some help.

0
source

Delete first lines from a Unicode html file

I can't access your file so I can't test this, but one of these should work:

gawk 'NR>5' Result.html>small2
perl -ne 'print if $.>5' Result.html>small2

If they don't work, I doubt it is a problem with the encoding, you may have some strange characters screwing things up. try passing your file through od to check:

od -c Result.html | more

UPDATE:

I see in the output of od -c that you have mac-style lines that end with a carriage return (\r) and not a line feed (\n). So, try changing these to \n and running sed or one of the other commands again:

perl -ne 's/\r/\n/g; print' Results.html | gawk 'NR>5' > small2

Also, please post your file so we can access it and try it ourselves. It will greatly speed up the process. The service you have linked to requires us to get an account.

0
source

running tail -f on a server which connects to another server over ssh

If you have netcat installed on server1.com (you probably do), you may want to use the ssh directive ProxyCommand to seamlessly hop across server1.com; thus, when you press Ctrl+C, it will only terminate the command on server2.com, not your SSH session.

Example of your ~/.ssh/config (create the file if it doesn't exist; append to end if it does):

Host server2.com
  User piskvor
  ProxyCommand ssh -q server1.com nc -q0 server2.com 22

What happens here:

  • ssh connects to server1.com
  • it remotely connects from there to server2.com (using nc)
  • which ferries the data through server1.com

This is completely transparent to your ssh client, so you can work with server2.com as if you were connected directly (e.g. SFTP, X forwarding, TCP forwarding, etc.)

For a more detailed explanation (as well as extending this to multiple hops), see this article, or this similar question on SU.

0
source

GUI for tail for Linux

MakeLogic Tail is one. The download link is acting a bit strange though. I managed to get the source code but I'm not familiar with how to compile Java code.

Home: http://www.makelogic.com/tail/TailHome.htm
Source: http://www.makelogic.com/downloads/MakeLogicTail2.1.0src.zip

Update

Played around with the URL a bit and found the jar file. Could just be me but it didn't want to start downloading when linked directly to. I managed to still get it and uploaded it to MediaFire.
Executable jar file: http://www.mediafire.com/?koc791k2bjjlfqb

description

Print the last 10 lines of each FILE to standard output. With more than one FILE, precede each with a header giving the file name. With no FILE, or when FILE is -, read standard input.

Mandatory arguments to long options are mandatory for short options too.
-c
, --bytes=K

output the last K bytes; alternatively, use -c +K to output bytes starting with the Kth of each file

-f, --follow[={name|descriptor}]

output appended data as the file grows; -f, --follow, and --follow=descriptor are equivalent

-F

same as --follow=name --retry

-n, --lines=K

output the last K lines, instead of the last 10; or use -n +K to output lines starting with the Kth

--max-unchanged-stats=N

with --follow=name, reopen a FILE which has not changed size after N (default 5) iterations to see if it has been unlinked or renamed (this is the usual case of rotated log files). With inotify, this option is rarely useful.

--pid=PID

with -f, terminate after process ID, PID dies

-q, --quiet, --silent

never output headers giving file names

--retry

keep trying to open a file even when it is or becomes inaccessible; useful when following by name, i.e., with --follow=name

-s, --sleep-interval=N

with -f, sleep for approximately N seconds (default 1.0) between iterations. With inotify and --pid=P, check process P at least once every N seconds.

-v, --verbose

always output headers giving file names

--help

display this help and exit

--version

output version information and exit

If the first character of K (the number of bytes or lines) is a ’+’, print beginning with the Kth item from the start of each file, otherwise, print the last K items in the file. K may have a multiplier suffix: b 512, kB 1000, K 1024, MB 1000*1000, M 1024*1024, GB 1000*1000*1000, G 1024*1024*1024, and so on for T, P, E, Z, Y.

With --follow (-f), tail defaults to following the file descriptor, which means that even if a tail’ed file is renamed, tail will continue to track its end. This default behavior is not desirable when you really want to track the actual name of the file, not the file descriptor (e.g., log rotation). Use --follow=name in that case. That causes tail to track the named file in a way that accommodates renaming, removal and creation.

copyright

Copyright © 2012 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.

reporting bugs

Report tail bugs to bug-coreutils[:at:]gnu[:dot:]org
GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
General help using GNU software: <http://www.gnu.org/gethelp/>
Report tail translation bugs to <http://translationproject.org/team/>


see also

The full documentation for tail is maintained as a Texinfo manual. If the info and tail programs are properly installed at your site, the command

info coreutils 'tail invocation'

should give you access to the complete manual.


author

Written by Paul Rubin, David MacKenzie, Ian Lance Taylor, and Jim Meyering.

How can this site be more helpful to YOU ?


give  feedback