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Full Discussion: Knowing when a different program modifies a file
Top Forums UNIX for Dummies Questions & Answers Knowing when a different program modifies a file Post 302795423 by SkySmart on Wednesday 17th of April 2013 04:49:44 PM
Old 04-17-2013
Quote:
Originally Posted by Don Cragun
I'm guessing that you're really saying that new lines being written to the log file did not show up in your vi editing buffer until you closed vi and reloaded the file. It is extremely unlikely that anything stopped writing to a file because vi had that file open.

When you edit a file using vi (or ex or ed or emacs or any other editor) you load a copy of that file into a buffer. You edit the buffer; not the underlying file. If you want to see recent additions to the file while you are editing it, you need to reload the buffer from the file. In vi, the command to reload the buffer is :e. If you have changed the buffer and have not written the updates back to another file; you'll need to use :e!. If you change the file and write those changes back to the file while some other process is writing to it, whether the changes you made to the file or additions added by that other process or some combination of those changes and additions will appear in the file after you exit vi is unspecified.
i'm pretty familiar with vi. what i was saying was that, apparently, when you vi a file thats being written to by syslog, syslog stops updating that file. yeah, when i vied that filed and saved it, i saw my additions in there. that wasn't the issue. the problem was, after my additions, i expected to have syslog continue to update the log file as usual. but no. it just stopped updating, until i restarted it.

this happened on linux red hat 6.2. i'm guessing most people aren't aware of this?
 

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LEARN ABOUT DEBIAN

battery-stats-collector

BATTERY-STATS-COLLECTOR(8)				      System Manager's Manual					BATTERY-STATS-COLLECTOR(8)

NAME

       battery-stats-collector - Collect statistics about battery charge

SYNOPSIS

       battery-stats-collector [option] ...

DESCRIPTION

       Does exactly as it says on the tin - it will collect information from the APM subsystem and write it to a log file.

       Normally battery-stats-collector will be invoked by the system startup scripts.

OPTIONS

       battery-stats follow the usual GNU command line syntax, with long options starting with two dashes (`-').

       -V, --version
	      Show version of battery-stats-collector and exit.

       -h, --help
	      Show summary of options and exit.

       -s, --syslog
	      Log  error  messages  to	syslog,  rather than stderr. Note that messages regarding invalid command line parameters will still go to
	      stderr.

       -o filename, --output filename
	      Append statistics to the given file. The default filename is /var/log/battery-stats

       -1, --once
	      Only collect a single sample and exit. The default is to loop continiously.

       -i seconds, --interval=seconds
	      Sampling intervals in seconds. If not specified, stats will be collected every 30 seconds.

       -I, --ignore-missing-battery
	      Keeps quiet about missing batteries. This stops the warnings on stderr/syslog that would otherwise occur when the battery  is  miss-
	      ing.

       -F samplecount, --flush=samplecount
	      Flushes  data  to  the logfile every <samplecount> samples. A value of zero turns off flushing altogether. If left unspecified, bat-
	      tery-stats-collector will assume a value of 1, i.e. flush at every write.  Setting the value too low will  tend  to  keep  the  disk
	      spinning (and use battery needlessly).  Setting the value too high will loose statistics in case of an improper shutdown.
	      Note  that  since  battery-stats-collector  uses the standard Ansi C library, data will still be flushed periodically (regardless of
	      this setting) once the buffer fills up. The size of the buffer is platform dependent, but 4Kb and 8Kb seem pretty normal.

FILES

       /var/log/battery-stats
	      Default file for writing battery charge samples to.

SEE ALSO

       battery-graph(1)
       Newer versions of this program may (or may not) be available at http://karl.jorgensen.com/battery-stats

AUTHOR

       This manual page was written by Karl E. Jorgensen <karl@jorgensen.com>, for the Debian GNU/Linux system (but may be used by others).

								September 18, 2002					BATTERY-STATS-COLLECTOR(8)
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