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

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5
votes
3answers
2k views

Is it fine to use tail -f on large log files

I would like monitor a large log file (close to 1 GB) for errors. I want this to be close to real time (few seconds delay is fine). My plan is to use tail -f | grep. Is there any performance issues ...
34
votes
8answers
17k 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 ...
24
votes
3answers
27k 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 ...
3
votes
2answers
5k views

Add carriage return to output of `tail` while using `grep`

I'm looking to refactor the following command: tail -f production.log | grep -e "Processing " -e "compatible;" -e "Completed in " -e This is the output of the command: Processing ...
6
votes
2answers
914 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 ...
4
votes
1answer
210 views

What's a convenient way of checking what's being added to a log file in realtime?

Right now I'm essentially executing tail /var/log/syslog manually every once in a while. Is there something that lets me see what's being added continuously, or do I need to write something myself?
18
votes
6answers
16k 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 ...
8
votes
2answers
10k 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 ...
4
votes
6answers
2k views

Is it possible to “roll” a symlink to a new file without affecting any open file handles?

An application I am developing locally logs it's output to files formatted with the current timestamp such as app-%Y%m%d.log. To make it simple to be able to tail the current's day log in a terminal ...
139
votes
17answers
72k 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 ...
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 ...
14
votes
7answers
17k 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.
24
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 ...