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

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0
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2answers
41 views

Monitor a logfile and execute different commands depending on different conditions

I have a logfile which I want to monitor and depending on which condition is met, different commands should be executed. I found a solution that comes close to this here. Unfortunately it doesn't ...
4
votes
2answers
91 views

How to tail a log file by time?

Say my log file(log.txt) is something like 2014-01-01 22:30:30 something happened.... 2014-01-01 22:30:31 something happened.... 2014-01-01 22:30:41 something happened.... I want to tail this file ...
1
vote
1answer
39 views

What is the reverse of tail -c +K?

I was reading this thread. The command tail -c +K /tmp/1 outputs bytes starting with the Kth of each file. From man tail -c, --bytes=K output the last K bytes; alternatively, use -c ...
2
votes
3answers
248 views

View only the new entries in a growing log file

tail -f x.log I use this command to see a growing log file in the command prompt. I am interested only in seeing the log lines that are written to the file after running tail -f and not interested ...
1
vote
1answer
58 views

Can someone explain this tail + line to me?

I'm looking through some of the scripts that are on the servers and came across an 80MB shell script. Naturally curious I decided to look in there and came across this line: tail +4802 $0 | zcat - | ...
0
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1answer
36 views

Clear terminal window before tail -f output

I have the following script running every 3 minutes with cron: #!/bin/bash cd ~/Documents/Fetch/ wget remotehost/data.txt --output-document=tmp cp tmp data.txt rm tmp To fetch a self-generated php ...
3
votes
2answers
92 views

Check if conditional with awk for matches in logfile

I want to check the auth.log file for accepted sshd connections and execute an action if any are found. Here is my code: tail -f /var/log/auth.log | awk '{ if($0 ~ /sshd/ && $0 ~ /Accepted/) ...
1
vote
1answer
47 views

tail -f error_log | cowsay

I'm watching the error logs on my local setup. I'd like to have the errors print out in cowsay, you know, for fun. tail -f error_log | cowsay doesn't work. Any ideas?
4
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3answers
201 views

Redirect the tail output to a file then stop when match found

there is this log file that data coming in is continuous. what i wanted to happen is to tail -f this log file then redirect it to a file with the ff conditions example of the log files content ...
4
votes
1answer
223 views

Does less have a feature like tail --follow=name (-F)

The command less can be used to replace tail in tail -f file to provide features like handling binary output and navigating the scrollback: less +F file The + prefix means "pretend I type that ...
4
votes
4answers
288 views

Make tail not modify the charset of the terminal

In a linux terminal (CentOS) I am using the command tail --follow=name my-rolling-file.log in order to see the logs of my application. Sometimes in the log there is some binary data dumped (I dump ...
2
votes
4answers
256 views

Show filename at begining of each line when tailing multiple files at once?

when tailing multiple files at once as shown below, is any there any way to show the file name at the start of each line? tail -f one.log two.log current output ==> one.log <== contents of ...
1
vote
1answer
44 views

“tail -f” in GNOME Terminal - scrolling to previous lines breaks if there's been lots of subsequent output

I'm viewing a log file with "tail -f" using GNOME Terminal. The log has a lot of input constantly coming into it, and what I find happens is that I scroll up to a previous section, and I'm reading ...
6
votes
1answer
213 views

Is `tail -f` more efficient than `less +F`?

This article pointed out some reasons to use less +F over tail -f. Most of the reasons are about the features, not technical reasons: less +F can highlight, search, navigate through file. How about ...
2
votes
2answers
93 views

Print file contents and delete the printed content* from the file

In Linux, from a bash shell, how can I print the contents of a file and remove the content I just printed content from the file? I have a program writing texts to a file repeatedly. On a Linux shell ...
2
votes
1answer
45 views

Is it possible to tail -f output to a single line?

less has an option -S or --chop-lines which prevents lines from wrapping and shows output as one line (often extended beyond screen). Is it possible to do this with tail -f? The tail man page ...
2
votes
3answers
198 views

Keep a tally from a log file

I have a file called output.log which has this content: Thread started Thread finished Thread started Thread finished Thread started Thread started I monitor its output using: tail -f output.log ...
0
votes
2answers
92 views

Will “tail -100 | sed -n 1p” only read one line?

I'm searching backwards from the end of a file, it's probably easiest to explain by showing my code: enough=0 numberOfLines=100 fileName="/path/to.file" # Tail the last $numberOfLines lines; if the ...
0
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0answers
26 views

how can I redirect the grepped output of tail -f to a file? [duplicate]

I want to do this: tail -f /var/log/apache2/access.log | grep 'POST \/review' But I want the output to go to a file and I want this to run constantly for a day or two. I tried a simple script ...
0
votes
1answer
58 views

tail-ing a filename that is a date [duplicate]

I am creating a logfile from kermit named the current date (which is in the format of DD MMM YYYY - which can not be changed AFAIK), and using the file name as today's date. I then have a Bash script ...
4
votes
5answers
479 views

Using head and tail to grab different sets of lines and saving into same file

So this is for homework, but I will not be asking the specific homework question. I need to use head and tail to grab different sets of line from one file. So like lines 6-11 and lines 19-24 and ...
0
votes
1answer
50 views

Use tail and grep to send an IRC message?

How do I use a command like: tail -f /home/user/log.txt | grep '!calladmin\|admin' To send an IRC message to me when !calladmin or admin are posted in the log? Or is there an easier way to do ...
-1
votes
1answer
59 views

Hash different, is it safe?

The first time I downloaded Tails image which is with different sha256sum than the webpage giving, so I downloaded it once again and this time it is correct. Then I unpakeged all the files inside the ...
0
votes
1answer
111 views

Pipe stdout to command on stdout

If I had a running process like tail -F watch.txt and I wanted to capture the stdout from this running process and pipe it to another command on stdout how could this be done? Here's an example of a ...
3
votes
2answers
182 views

Repeatedly execute bash command while there's no output from another process

I'm running fs_usage to detect access to an object on my filesystem. sudo fs_usage -w | grep -E 'object' I now want to run a touch command on that object every 5 seconds as long as there's no new ...
3
votes
2answers
237 views

Coloring tail output with perl

tail -f logfile.log | perl -pe 's/.*foo*/\e[1;41m$&\e[0m/g' will color all the lines containing the pattern "foo" in the logfile.log file. How can I make use of this in order to highlight ...
2
votes
2answers
33 views

Getting transient PID from log into a PS search before it dies

I have a transient prelink process populating our audit log, but we're not sure what the process is. The error log gives us the PID, but it disappears pretty much instantly, as the process finishes ...
5
votes
2answers
3k views

Negative arguments to head / tail

Variants of this question have certainly been asked several times in different places, but I am trying to remove the last M lines from a file without luck. The second most voted answer in this ...
6
votes
3answers
2k views

Suppress 'file truncated' messages when using tail

I'm tailing a log file using tail -f messages.log and this is part of the output: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Fusce eget tellus sit amet odio porttitor rhoncus. Donec ...
0
votes
0answers
58 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 ...
2
votes
1answer
686 views

splitting a CSV and keeping the header without intermediate files [closed]

I am trying to split a dozen 100MB+ csv files into managable smaller files for a curl post. I have managed to do it but with a lot of temporary files and IO. It's taking an eternity. I am hoping ...
3
votes
1answer
668 views

grep not working in a for loop over a list

I have some log files. And I have a list of user ids. My log files are in a particular format log-yyyy-mm-dd e.g. log-2014-09-30 I am trying to search each userId in the log file. This is what I am ...
4
votes
3answers
271 views

Time required to do pipe output to head/tail [duplicate]

There are lots of txt files in a directory. If I do time wc -l *.txt | head it takes real 0m0.032s user 0m0.020s sys 0m0.008s If I do time wc -l *.txt | tail it takes real 0m0.156s ...
6
votes
1answer
3k views

Tail log file on multiple machines over ssh

I'm trying to tail a log file on multiple remote machines and forward the output to my local workstation. I want connections to close when pressing Ctrl-C. At the moment I have the following function ...
5
votes
3answers
405 views

Open a directory and let it update itself using “tail -f”

Similar to my last question: Open a text file and let it update itself; is there a way I could do the same but for a folder instead? As I have a log folder, can I use tail -f with a folder? i.e. $ ...
2
votes
2answers
335 views

cygwin, tail -F and rapidly filling/rotatinglogs

I'm using cygwin tail to follow busy java web application logs, on a windows server, generating roughly 16Gb worth of logs a day. I"m constrained to 10MB log sizes, so the files roll very often. ...
27
votes
4answers
2k views

Why does “tail -f … | tail” fail to produce any output?

Why does the following command not produce any output? $ tail -f /etc/passwd | tail After reading about buffering, I tried the following to no avail: $ tail -f /etc/passwd | stdbuf -oL tail Note ...
10
votes
3answers
1k views

Open a text file and let it update itself

How can I open a text file and let it update itself? Similar to the way top works. I want to open a log file and watch it update itself on the fly. I have just tried: $ tail error.log But just ...
2
votes
4answers
490 views

Only cat from specific line X (with a pattern) to other specific line Y (with a pattern)

A little extended problem from "cat line x to line y on a huge file": I have a huge file (2-3 GB). I'd like to cat/print only from the line having "foo:" to the line having "goo:". Assume that "foo:" ...
1
vote
3answers
93 views

Pulling lines n to m from list of files found

Ultimately I need to grab lines 3-53 from ever csv in each subdirectory. I grabbed the lines like so (cat isn't necessarily required): cat /[path]/[file].csv | head -53 | tail -51 And the files ...
3
votes
1answer
298 views

“tail -f” show old file after file has been rotated [duplicate]

I have a script running continuously, reading tail -f /var/log/daemon.log The problem is, when the file /var/log/daemon.log gets rotated by logrotate, tail still has "file handle" for the old ...
19
votes
2answers
1k views

Coloring different sources for tail

I'm watching different logs by tail -q -f /var/log/syslog -f /var/log/fail2ban.log -f /var/log/nginx/error.log How can I have the output of each log colored differently?
8
votes
3answers
3k views

How to tail multiple files using tail -0f in Linux/AIX

I tried tailing two files using the option: tail -0f file1.log -0f file2.log In Linux I see an error "tail : can process only one file at a time". In AIX I see the error as "Invalid options". ...
8
votes
0answers
274 views

scroll through output using `less` or `tail -f` while keeping the header visible [duplicate]

I am trying to scroll through some data formatted thus- NFI T[PSEC] T[K] EKIN(PSI) E(RHO) ECONS ANNEE ANNER !> 1 0.00012 0 0.45873 16.26904 16.72777 ...
6
votes
1answer
114 views

Not able to see the progression of a file with “tail -f”!

It's a surprise why now this command isn't working which earlier was. See I've the below command to run for backup. ubuntu@ubuntu:~$ sudo tar -cvf /media/ubuntu/My*Linux/ub*data/zebra.tar ...
4
votes
1answer
116 views

tail -f produces no output in Ubuntu live CD

For some test I start Ubuntu Live from USB. I'm trying to use tail command to show debug log, but it doesn't work. I also test opening two terminals (t1, t2) with this code: t1: touch a t2: ...
3
votes
1answer
189 views

Grep with spaces suddenly doesn't work

When performing a grep like: $ tail -f apilog_2014.07.09.log | grep "HELLO" | grep "99999" I get the desired output: 12:22:35 server apache2: HELLO FRIEND 99999 12:22:35 server apache2: HELLO ...
2
votes
1answer
340 views

multitail - custom config (multitail.conf) location

Is it possible to provide a custom location for multitail.conf - or are my only options /etc/multiltail.conf or ~/multitail.conf? I'd like to provide a specific config file that has regexes specific ...
2
votes
3answers
348 views

What does “tail -f ” do? [duplicate]

I don't understand the function of the option -f added to the tail command. I know that tail views the "last" part of a file. The manual says that -f outputs appended data as the file grows But ...
15
votes
3answers
2k views

How do I “cat and follow” a file?

A file is being sequentially downloaded by wget. If I start unpacking it with cat myfile.tar.bz2 | tar -xj, it may unpack correctly or fail with "Unexpected EOF", depending on what is faster. How to ...