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chrisale
Joined: 09 Nov 2005
Posts: 187
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 Posted: Sun Dec 18, 2005 9:55 pm Post subject: Dealing with timestamped images |
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I've added some satellite, jetstream and radar images to my frontpage.
The first two were easy, the radar was a bit more involved because rather than simply updating a single temporary image, Enviroment Canada stores the temporary radar images individually, by time, every 10 minutes.
SO I had to create a UNIX shell script running "sed" to search and replace the URL of the image every 10 minutes. Once I figured out the regular expression to do it... it was fairly straight forward, the hardest part was dealing with the time formats that get their zeros stripped off after doing a math operation on them.
Anyway. Here's the shell script, I run it in a cron job on the 10s and the output goes to a log file:
| Code: |
#/bin/sh
## First grab dates in UTC format (-u operator). Minute and Hour must
## be in double digit format.
curyear=`date -u +%G`
curday=`date -u +%d`
curmonth=`date -u +%m`
curhour=`date -u +%H`
curminute=`date +%M`
#Store filename prefix and extension
preword='XSI_CAPPI_'
postword='.GIF'
#Store modulus of the current minute.
#We will only update every 10 minutes on the 10s.
#Radar image is delayed by about 10 minutes..
#thus we'll subtract 10 from current minute.
#Also, in case its' the top of the hour, we'll need to store the previous hour.
minmod10=`expr "$curminute" % 10`
oldminute=`expr "$curminute" - 10`
prevhour=`expr "$curhour" - 1`
echo ''
echo 'Starting Radar Script'
echo 'Current UTC Time'
echo "$curyear-$curmonth-$curday,$curhour:$curminute"
if ( test $minmod10 -eq 0 )
then
if ( test "$curhour" -le 10 )
then
case "$oldminute" in
-10)
if ( test "$prevhour" -le 10 )
then
sed 's/'"$preword"'\(.\)\{4\}_\(.\)\{2\}_\(.\)\{2\}_\(.\)\{2\}_\(.\)\{2\}'"$postword"'/'"$preword$curyear"'_'"$curmonth"'_'"$curday"'_0'"$prevhour"'_50'"$postword"'/g' /etc/wview/html/index.htx > /etc/wview/html/temp
mv /etc/wview/html/temp /etc/wview/html/index.htx
echo 'Its top of hour, and GMT is less than or equal to 10. We need to add a 0 to the hour.'
else
sed 's/'"$preword"'\(.\)\{4\}_\(.\)\{2\}_\(.\)\{2\}_\(.\)\{2\}_\(.\)\{2\}'"$postword"'/'"$preword$curyear"'_'"$curmonth"'_'"$curday"'_0'"$prevhour"'_50'"$postword"'/g' /etc/wview/html/index.htx > /etc/wview/html/temp
mv /etc/wview/html/temp /etc/wview/html/index.htx
echo 'Its top of hour, and GMT is greater than 10. So we need the prevhour but no 0 before.'
fi
;;
0)
sed 's/'"$preword"'\(.\)\{4\}_\(.\)\{2\}_\(.\)\{2\}_\(.\)\{2\}_\(.\)\{2\}'"$postword"'/'"$preword$curyear"'_'"$curmonth"'_'"$curday"'_0'"$curhour"'_00'"$postword"'/g' /etc/wview/html/index.htx > /etc/wview/html/temp
mv /etc/wview/html/temp /etc/wview/html/index.htx
echo 'Its 10 minutes past. So replace the single 0 in oldminute with double 00 instead'
;;
*)
sed 's/'"$preword"'\(.\)\{4\}_\(.\)\{2\}_\(.\)\{2\}_\(.\)\{2\}_\(.\)\{2\}'"$postword"'/'"$preword$curyear"'_'"$curmonth"'_'"$curday"'_0'"$curhour"'_'"$oldminute$postword"'/g' /etc/wview/html/index.htx > /etc/wview/html/temp
mv /etc/wview/html/temp /etc/wview/html/index.htx
echo 'Its somewhere between 20 and 50 this is the easy part.'
;;
esac
else
case "$oldminute" in
-10)
if ( test "$prevhour" -le 10 )
then
sed 's/'"$preword"'\(.\)\{4\}_\(.\)\{2\}_\(.\)\{2\}_\(.\)\{2\}_\(.\)\{2\}'"$postword"'/'"$preword$curyear"'_'"$curmonth"'_'"$curday"'_0'"$prevhour"'_50'"$postword"'/g' /etc/wview/html/index.htx > /etc/wview/html/temp
mv /etc/wview/html/temp /etc/wview/html/index.htx
echo 'Its top of hour, and GMT is less than or equal to 10. We need to add a 0 to the hour.'
else
sed 's/'"$preword"'\(.\)\{4\}_\(.\)\{2\}_\(.\)\{2\}_\(.\)\{2\}_\(.\)\{2\}'"$postword"'/'"$preword$curyear"'_'"$curmonth"'_'"$curday"'_'"$prevhour"'_50'"$postword"'/g' /etc/wview/html/index.htx > /etc/wview/html/temp
mv /etc/wview/html/temp /etc/wview/html/index.htx
echo 'Its top of hour, and GMT is greater than 10. So we need the prevhour but no 0 before.'
fi
;;
0)
sed 's/'"$preword"'\(.\)\{4\}_\(.\)\{2\}_\(.\)\{2\}_\(.\)\{2\}_\(.\)\{2\}'"$postword"'/'"$preword$curyear"'_'"$curmonth"'_'"$curday"'_'"$curhour"'_00'"$postword"'/g' /etc/wview/html/index.htx > /etc/wview/html/temp
mv /etc/wview/html/temp /etc/wview/html/index.htx
echo 'Its 10 minutes past. So replace the single 0 in oldminute with double 00 instead'
;;
*)
sed 's/'"$preword"'\(.\)\{4\}_\(.\)\{2\}_\(.\)\{2\}_\(.\)\{2\}_\(.\)\{2\}'"$postword"'/'"$preword$curyear"'_'"$curmonth"'_'"$curday"'_'"$curhour"'_'"$oldminute$postword"'/g' /etc/wview/html/index.htx > /etc/wview/html/temp
mv /etc/wview/html/temp /etc/wview/html/index.htx
echo 'Its somewhere between 20 and 50 this is the easy part.'
;;
esac
fi
echo 'done sed'
else
echo 'Nothing to do.'
fi
echo 'Changing Permissions'
chmod 775 /etc/wview/html/index.htx
echo done
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bhnb
Joined: 28 Nov 2005
Posts: 127
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| Posted: Mon Dec 19, 2005 6:08 pm Post subject: |
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Hi Chris
It's probably over-cautious for this application but I always try to make just one call to 'date' so that the results are consistent, and the day/minute/month/year/whatever hasn't rolled over between the first and last calls.
This would set your variables in a safer way:
eval "`date -u "+curyear=%Y curday=%d curmonth=%m curhour=%H curminute=%M"`"
It's based on the example at http://cfaj.freeshell.org/shell/tuesday-tips/#tt-2004-06-29
Cheers
Jon |
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chrisale
Joined: 09 Nov 2005
Posts: 187
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| Posted: Wed Dec 21, 2005 10:42 am Post subject: |
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I never thought of that... good suggestion, I'll add that in.
I've also debugged the script a lot now that it's had a chance to go through a few daily cycles... I'll update the code above when I'm 99% sure it's "stabilized", that said the code above is 90% functional. |
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