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I want to know how to tail a log file when lines in the files are updating(appending and removing)?

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As Atari911 said, you can use watch along with cat to do this. Use

watch cat <filename>

this will output the contents of the file given by filename every 2 seconds to standard output. To change the interval for updating the output to something like 1 second(you can't reduce beyond 0.1), you can use

watch -n 1 cat <filename>

I am using cat to output the complete file, you could tail but that would only give you the last n lines of the file, where n is 10 by default.

Refer to the manual page of watch for more info.

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You might try:

tail -f /var/log/syslog

Or whatever file you are interested in. Get out of 'tail' with Ctrl+c.

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  • This is not working when lines are removing from the file – Lasith Malinga Jan 27 '14 at 15:58
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    I am unaware of any log file where lines are removed. Which is it? – chili555 Jan 27 '14 at 16:02
  • It's relevant to my application – Lasith Malinga Jan 27 '14 at 16:05
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You need to use the tail command which output the last part of files in real time including all incoming logs to a standard output device such as screen. the commadn to use is

tail -f /path/to/log/file

EDIT: TRY this

tail -f --retry /path-to-log-file

This will try to reopen the file with the new contents

Or this

tail -F /path/to/log/file
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  • This is not working when lines are removing from the file – Lasith Malinga Jan 27 '14 at 16:00
  • @LasithMalinga check the edit – Maythux Jan 27 '14 at 16:09
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I'm not sure exactly what you are trying to do but you could use the watch command in conjunction with the tail command... Something like this:

watch tail /path/to/file

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