File name with yyyymmddhhmi Post: 303019989

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Top Forums UNIX for Beginners Questions & Answers File name with yyyymmddhhmi Post 303019989 by rbatte1 on Wednesday 11th of July 2018 01:30:25 PM

07-11-2018

Moderator

You also need to ensure that your file creation and all the output being put into it is Atomic, i.e. a single operation that takes a single IO. Often this is done by creating the file and building it up with content as another name and then when it is ready, renaming it to it appears as a complete file instantly.

If you have a file that takes even a whole second to build, then you may sometimes be unlucky and fetch a partial file.

Something like this would illustrate it:-

Code:

((random_delay=$RANDOM%9))

( sleep $random_delay ; cat /tmp/myfile ) &      # Display the file at some undetermined time

date                             > /tmp/myfile
echo "First data line of file"  >> /tmp/myfile
sleep 3
echo "Second data line of file" >> /tmp/myfile
sleep 3
echo "Last data line of file"   >> /tmp/myfile
wait                                             # In case the random delay is long, wait for the background sleep/cat to finish

If you run this repeatedly, you may get 1, 2 or 3 lines of output. You can compensate by the cat reading a file that is always the finished article, so more like:-

Code:

((random_delay=$RANDOM%9))

( sleep $random_delay ; cat /tmp/finalfile ) &   # Display the file at some undetermined time

date                             > /tmp/myfile
echo "First data line of file"  >> /tmp/myfile
sleep 3
echo "Second data line of file" >> /tmp/myfile
sleep 3
echo "Last data line of file"   >> /tmp/myfile

mv /tmp/myfile /tmp/finalfile                    # Atomic file write
wait                                             # In case the random delay is long, wait for the background sleep/cat to finish

It may fail first time if the file does not exist, but afterwards it would only ever read a completed file.

Doing this, you could also make a link as a "latest" file, so you always know which one to pick up.

I hope that this helps,
Robin

rbatte1

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LEARN ABOUT DEBIAN

ifpps

ifpps(8)							netsniff-ng-toolkit							  ifpps(8)

NAME

       ifpps - fetch and format kernel network statistics

SYNOPSIS

       ifpps	 -d|--dev <netdev> [-t|--interval <sec>][-p|--promisc][-c|--term]
	    [-C|--csv][-H|--csv-tablehead][-l|--loop][-v|--version][-h|--help]

DESCRIPTION

       A tiny tool to provide top-like reliable networking statistics.	ifpps reads out the 'real' kernel statistics, so it does not give
       erroneous statistics on high I/O load.

OPTIONS

       ifpps --dev eth0
	   Fetch eth0 interface statistics.

       ifpps --dev eth0 --interval 60 --csv
	   Output eth0 interface statistics every minute in CSV format.

OPTIONS

       -h|--help
	   Print help text and lists all options.

       -v|--version
	   Print version.

       -d|--dev <netdev>
	   Device to fetch statistics for i.e., eth0.

       -p|--promisc
	   Put the device in promiscuous mode

       -t|--interval <time>
	   Refresh time in sec (default 1 sec)

       -c|--term
	   Output to terminal

       -C|--csv
	   Output in CSV format.  E.g. post-processing with Gnuplot et al.

       -H|--csv-tablehead
	   Print CSV table head.

       -l|--loop
	   Loop terminal output.

AUTHOR

       Written by Daniel Borkmann <daniel@netsniff-ng.org>

DOCUMENTATION

       Documentation by Emmanuel Roullit <emmanuel@netsniff-ng.org>

BUGS

       Please report bugs to <bugs@netsniff-ng.org>

								    2012-06-29								  ifpps(8)