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

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146
votes
17answers
80k 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 ...
87
votes
3answers
5k views

Does tail read the whole file?

If I want to tail a 25 GB textfile, does the tail command read the whole file? Since a file might be scattered on a disk I imagine it has to, but I do not understand such internals well.
55
votes
6answers
94k 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 ...
49
votes
1answer
10k 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 ...
40
votes
4answers
82k views

How to monitor only the last n lines of a log file?

I have a growing log file for which I want to display only the last 15 lines. Here is what I know I can do: tail -n 15 -F mylogfile.txt As the log file is filled, tail appends the last lines to the ...
34
votes
8answers
18k views

How to obtain inverse behavior for `tail` and `head`?

Is there a way to head/tail a document and get the reverse output; because you don't know how many lines there are in a document? I.e. I just want to get everything but the first 2 lines of foo.txt ...
27
votes
4answers
3k 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 ...
27
votes
3answers
30k views

How does the “tail” command's “-f” parameter work?

$ tail -f testfile the command is supposed to show the latest entries in the specified file, in real-time right? But that's not happening. Please correct me, if what I intend it to do is wrong... I ...
26
votes
1answer
2k 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 ...
25
votes
2answers
7k views

The 'less' command-line equivalent of 'tail -f'

I would like to open up a file using less, and have it automatically scroll the file similar to tail -f. I know that I can do less file, and then hit Shift-F to forward forever; like tail -f. I need ...
25
votes
4answers
7k views

monitor files (ala tail -f) in an entire directory (even new ones)

I normally watch many logs in a directory doing tail -f directory/*. The problem is that a new log is created after that, it will not show in the screen (because * was expanded already). Is there a ...
21
votes
3answers
21k views

Piping from grep to awk not working

I am trying to grep the ongoing tail of file log and get the nth word from a line. Example file: $ cat > test.txt <<EOL Beam goes blah John goes hey Beam goes what? John goes forget it Beam ...
20
votes
9answers
40k 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. ...
20
votes
4answers
8k 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 ...
19
votes
2answers
2k 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?
18
votes
5answers
13k 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 ...
18
votes
6answers
18k 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 ...
18
votes
6answers
3k 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.
18
votes
4answers
19k 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 ...
17
votes
7answers
18k views

grep and tail -f?

Is it possible to do a tail -f (or similar) on a file, and grep it at the same time? I wouldn't mind other commands just looking for that kind of behavior.
17
votes
3answers
3k 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 ...
16
votes
4answers
3k views

How to do a continous 'wc -l' with gnu texttools?

I know of course that cat logfile.txt | wc -l 120 will tell me the number of lines in a file. Whereas tail -f logfile.txt will show me the new lines that another program writes to logfile.txt. ...
15
votes
4answers
1k views

How can I see the whole file and also wait for more data to be added to that file?

I want to read whole file and make it waiting for input, just like tail -f but with the complete file displayed. The length of this file will always change, because this is a .log file. How can I ...
14
votes
5answers
6k 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". ...
13
votes
3answers
5k 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 ...
13
votes
2answers
2k views

“tail -f | iconv -fsjis” does not output anything

I want to tail -f a file, but its content is in sjis encoding, so I need to have it converted to the native (utf-8) encoding of my terminal. When I do tail -f x | iconv -fsjis there will be no ...
12
votes
1answer
829 views

How to do `head` and `tail` on null-delimited input in bash?

find command can output names of files as a null-delimited strings (if -print0 is provided), and xargs can consume them with -0 option turned on. But in between, it's hard to manipulate that ...
12
votes
1answer
6k 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 ...
11
votes
2answers
362 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 ...
11
votes
1answer
2k views

How do I make a shell script that sends output to a process

I'm currently running a server console program in a screen because I need to both read it and occasionally send commands. I'd like to run the app as a deamon in the background (start/stop it with ...
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 ...
10
votes
4answers
885 views

What is the easiest way to execute text from tail at the command line?

Sometimes I'm working on a new (ubuntu) box and I type git and am alerted: The program 'git' is currently not installed. You can install it by typing: apt-get install git-core If that happens I ...
9
votes
4answers
6k 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 ...
9
votes
1answer
6k views

Observe multiple log files in one output

Is there an easy way to do something like tail -f mylogfile but to have the changes of more than one file displayed (maybe with the file name added as prefix to each line)? Or maybe a GUI tool? I am ...
9
votes
1answer
1k views

How to have tail -f show colored output with vim?

In this question, Gilles answered Yet another possibility is to run tail -f in an Emacs shell buffer and use Emacs's syntax coloring abilities. Because I'm a vim user, I'd like to do this with ...
8
votes
3answers
4k views

How can I do the equivalent of tail -f with ls? [duplicate]

Possible Duplicate: Is it possible to follow a command (run repeatedly)? as one would follow a file using tail -f? I would like to monitor files that are being downloaded to a directory in ...
8
votes
2answers
11k views

Reading from a continuously changing logfile [duplicate]

There is /location/of/thefile, which is a continuously changing logfile. The average density of refreshes is 4 per minute, the possible maximal refresh rate could be 30-40 per minute. Every refresh ...
8
votes
1answer
768 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 ...
8
votes
0answers
277 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 ...
7
votes
1answer
3k 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 ...
7
votes
1answer
5k views

How to follow (a la “tail -f”) a binary file from the beginning?

Is it possible to follow a binary file from the beginning, a la tail -f? This is useful in some cases, for example if I'm scping a file to a remote server, and at the same time I want to feed it to ...
7
votes
1answer
172 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 ...
6
votes
4answers
25k 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?
6
votes
3answers
4k 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 ...
6
votes
2answers
1k views

Is it possible to follow a command (run repeatedly)? as one would follow a file using tail -f?

I have a script which produces a file 'Detail.out'. I know that the script is completed whenever the file contains a certain number of lines (roughly 21025). So I find myself sitting at the command ...
6
votes
4answers
4k views

is there an alternative to tail -f that has convenient scrolling? [duplicate]

I'm usually inside GNU Screen or tmux, and that doesn't give me great scrolling functionality. Is there an alternative to tail -f that allows me to quickly scroll up? A tool that is like most is to ...
6
votes
1answer
1k 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 ...
5
votes
2answers
12k views

How to use tail -f with grep to show surrounding lines

I would like to see the output in a logfile greped by only one domain but also the following two lines. Example: tail -f /var/log/apache2/modsec_audit.log |grep mydomain.de this shows all lines, ...
5
votes
2answers
244 views

Command to remove the first N number of lines in input

Background I am running an SSH server and have this user that I want to delete. I cannot delete this user because he is currently running a few processes that I need to kill first. This is the ...
5
votes
3answers
1k 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 ...