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

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32
votes
1answer
4k views

How to do a `tail -f` of log rotated files?

On a long running system I usually have a terminal with $ tail -f /var/log/kern.log or something like this open. But from time to time I have to restart such command because no new messages are ...
28
votes
5answers
37k views

cat line X to line Y on a huge file

Say I have a huge text file (>2GB) and I just want to cat the lines X to Y (e.g. 57890000 to 57890010). From what I understand I can do this by piping head into tail or viceversa, i.e. head -A ...
4
votes
3answers
54 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 ...
5
votes
1answer
73 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 ...
2
votes
2answers
36 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. ...
26
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 ...
4
votes
3answers
306 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. $ ...
9
votes
3answers
836 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
274 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
82 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 ...
5
votes
1answer
170 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 ...
18
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?
5
votes
3answers
107 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
271 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 ...
9
votes
4answers
2k views

How do I make Vim behave like “tail -f”?

I would like to know if there is a way to make Vim behave like tail -f. Even the best Vim plugin I've found so far doesn't do what I expect. I really want to see the file update in real-time. Even ...
7
votes
5answers
2k views

Output file contents while they change

I want to output a file's contents while they change, for example if I have the file foobar and I do: magic_command foobar The current terminal should display the file's contents and wait until, I ...
5
votes
1answer
68 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 ...
24
votes
1answer
837 views

Do I need to worry about “tail: unrecognized file system type 0xbeefdead”?

I'm trying to follow a regular text file with tail -f -n 50 filename. I get the information from the file just fine, except I always get this error message: tail: unrecognized file system type ...
3
votes
1answer
89 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
2answers
2k views

How to execute this particular shell command from Python?

OK, so, I have this non-functional shell script, which I am rewriting piece by piece in python, except I am getting an "unexpected "|" error" from the shell (see below): #/bin/sh LINES=`cat $@ | wc ...
4
votes
1answer
63 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: ...
93
votes
13answers
35k views

How to have tail -f show colored output

I'd like to be able to tail the output of a server log file that has messages like: INFO SEVERE etc, and if it's SEVERE, show the line in red; if it's INFO, in green. What kind of alias can I ...
3
votes
2answers
934 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
72 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
70 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 ...
14
votes
2answers
1k 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 ...
1
vote
1answer
42 views

How to echo from specific line of a file to another specific line [duplicate]

Assume I have a file with about 10000 lines. How can I print 100 lines, starting from line 1200 to line 1300?
4
votes
2answers
490 views

continuous reading from named pipe (cat or tail -f)

I have configured rsyslog to log certain log events to /dev/xconsole: *.*;cron.!=info;mail.!=info |/dev/xconsole /dev/xconsole is a named pipe (fifo). If I want to see what is being logged, I ...
6
votes
3answers
2k views

Follow a pipe using less?

Can less follow (by pressing F) a piped input (similarly to a file)? For a file that is being written to, the command less <file> will follow the file when pressing F. But if I have a ...
4
votes
4answers
381 views

How to get lines 10 to 100 from a 200 line file into a new file [duplicate]

I have file with 200 lines. I need to extract lines from 10 to 100 and put them into a new file. How do you do this in unix/Linux? What are the possible commands you could use?
17
votes
6answers
2k views

Is there a way to make tail -F beep?

Is there a way to make tail -F or less beep (ring the bell in a terminal) when new data comes in (a new line is added to the file). Or is there any other unix utility to do this on a linux or mac.
1
vote
2answers
77 views

Temporarily freeze a process upon shell interaction

Let's say on a single console I have tail -F running, showing the output of many log files in realtime. Sometimes I need to run commands there too, however, and examine their output briefly, without ...
3
votes
2answers
47 views

tail display whole file and then only changes [duplicate]

My Linux version is 2.6.32-47-server (gcc version 4.4.3 (Ubuntu 4.4.3-4ubuntu5.1) ) #109-Ubuntu SMP Tue May 7 02:17:05 UTC 2013 I am currently doing a tail -f file and life is good. But that only ...
6
votes
4answers
2k views

`tail -f` until text is seen

I've got a CI server with a command-line interface that allows me to remotely kick-off a job (jenkins CI server and the jenkins-cli.jar tool). After I kick the job off I tail -f the log (sorry for ...
0
votes
1answer
60 views

Is it possible to `tail -f /dev/vcs`?

I would like to get a continuous stream of output from the virtual terminal. Is that possible? If not, why is tail -f not working here?
2
votes
3answers
349 views

Exception handling when using tail -f to monitor a log

I have a main script calling the script to do the monitoring. I am trying to catch the exception that the log is missing or not accessible anymore. tail -f is used instead of -F since the logs are ...
5
votes
3answers
360 views

tail -f, Determine if a file is no longer being written to [closed]

I am using tail -f to follow the growth of a log file. I am having trouble finding a way to detect if the process that is writing to the log file (when it crashes or is otherwise terminated) is no ...
13
votes
6answers
6k views

Best way to follow a log and execute a command when some text appears in the log

I have a server log that outputs a specific line of text into its log file when the server is up. I want to execute a command once the server is up, and hence do something like the following: tail -f ...
4
votes
2answers
574 views

What does tail -f <directory name> do?

I mistakenly executed the following command in the terminal: tail -f /logs/applications/logs* I got the following output: tail: file shrunk! Error 0 I am not sure what exactly happened. I have ...
2
votes
2answers
208 views

What does tail -0a do?

In the documentation for logstash, they mention the command tail -0a I have never heard of the -a flag and I can't find any information on google, tail --help or the man pages. What is the ...
1
vote
1answer
212 views

Convert newlines to null-delimited when using tail

How can I change the output from tail to use null-terminated lines instead of newlines? My question is similar to this one: How to do `head` and `tail` on null-delimited input in bash?, but differs ...
17
votes
8answers
16k views

Command to display first few and last few lines of a file

I have a file with many rows, and each row has a timestamp at the starting, like [Thread-3] (21/09/12 06:17:38:672) logged message from code..... So, I frequently check 2 things from this log file. ...
0
votes
3answers
80 views

Is it possible to change the default COUNT value of tail and head?

The less command accepts its defaults with an environment variable LESS, so you can export LESS='-F -g -i -M -R -S -w -X -z-4' at the beginning of your session. Is it possible to change the ...
1
vote
2answers
376 views

will tail with piping read whole file?

I want to read a big log file with 10000 lines everytime. and I use this command: tail -c +offset somefile | head -n 10000 my question is, with the piping of head, will tail read the whole file? ...
1
vote
1answer
346 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 ...
0
votes
1answer
67 views

Need to grep for specific lines from ongoing log and save it in some file

So, let me start with the overall outcome that i want to achieve. There is just one log, which will have info on certain devices, that i am upgrading. I use "tailf log" to monitor the log. Now, ...
8
votes
4answers
2k views

Grep from the end of a file to the beginning

I have a file with about 30.000.000 lines (Radius Accounting) and I need to find the last match of a given pattern. The command: tac accounting.log | grep $pattern gives what I need, but it's too ...
10
votes
2answers
216 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
2answers
48 views

Can less load lines which were appended to a file after opening?

When I am viewing a log file in less is it possible to make less reload the file to get lines which were appended to that file since it was opened?
0
votes
1answer
64 views

Stop tailing log

I have a problem, I accidentally did tail -f on a log, but now I cant quit! - Its the anaconda log during a redhat install. Control-C doesn't seem to work, I guess due to it saying sh: no job control ...