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

bb-csvinfo.cgi

BB-CSVINFO.CGI(1)					      General Commands Manual						 BB-CSVINFO.CGI(1)

NAME

       bb-csvinfo.cgi - CGI program to show host information from a CSV file

SYNOPSIS

       bb-csvinfo.cgi

DESCRIPTION

       bb-csvinfo.cgi  is  invoked  as	a CGI script via the bb-csvinfo.sh CGI wrapper.  Based on the parameters it receives, it searches a comma-
       separated file for the matching host, and presents the information found as a table.

       bb-csvinfo.cgi is passed a QUERY_STRING environment variable with the following parameters:

	  key (string to search for, typically hostname)
	  column (columnnumber to search - default 0)
	  db  (name of the CSV database file in $BBHOME/etc/, default hostinfo.csv)
	  delimiter (delimiter character for columns, default semi-colon)

       CSV files are easily created from e.g. spreadsheets, by exporting them in CSV format. You should have one host per  line,  with	the  first
       line  containing  the  column headings. Despite their name, the default delimiter for CSV files is the semi-colon - if you need a different
       delimiter, invoke bb-csvinfo.cgi with the "delimiter=<character>" in the query string.

Example usage
       This example shows how you can use the bb-csvinfo CGI. It assumes you have a CSV-formatted file with information about the hosts stored	as
       $BBHOME/etc/hostinfo.csv, and the hostname is in the first column of the file.

       Use with the bbgen --docurl
	      The  --docurl  option to bbgen(1) sets up all of the hostnames on your Xymon webpages to act as links to a CGI script. To invoke the
	      bb-csvinfo CGI script, run bbgen with the option

		 --docurl=/cgi-bin/bb-csvinfo.sh?db=hostinfo.csv&key=%s

SEE ALSO

       bb-hosts(5), hobbitserver.cfg(5), bbgen(1)

Xymon							    Version 4.2.3:  4 Feb 2009						 BB-CSVINFO.CGI(1)