Re: tail --retry not re-attempting to open file (original) (raw)

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From: Bernhard Voelker
Subject: Re: tail --retry not re-attempting to open file
Date: Wed, 03 Apr 2013 00:17:56 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130307 Thunderbird/17.0.4

As the following is contradicting the "Subject:" line, I'm assuming you meant the "--retry not re-attempting to open" variant.

On 04/02/2013 08:55 PM, Noel Morrison wrote:

tail --retry -f {FILE} or tail -f --retry {FILE} does continue to try to open the file. I just compiled 8.21 CoreUtils and found that the problem is still present.

Thank you for the report. However, I believe it is a result of a misinterpretation of tail's options.

As you can read from the --help output and - more thoroughly - in the texinfo documentation, tail -f --retry FILE is following the content of FILE by file descriptor:

-f, --follow[={name|descriptor}] output appended data as the file grows; -f, --follow, and --follow=descriptor are equivalent -F same as --follow=name --retry [...] --retry keep trying to open a file even when it is or becomes inaccessible; useful when following by name, i.e., with --follow=name

Once "tail -f" holds a handle to the open file descriptor, it will not try to reopen the file again. Instead, it uses polling or inotify (depending on the underlying file system) to follow the content of the file.

Furthermore, you get the following warning when --retry is used together with -f (or --follow=descriptor):

$ tail -f --retry /dev/null tail: warning: --retry is useful mainly when following by name ^C

Does that answer your question?

My 1st official report of any bugs.

BTW: the address address@hidden is the main discussion list which is used for general questions and discussions, while real bug reports would go to address@hidden. An email to the latter opens a new bug report in our bug tracking system and therefore makes it easier to follow bugs; OTOH this induces some overhead regarding status tracking which is not suitable for general discussions.

Have a nice day, Berny