1. Running the Operational Codes for the Brahmaputra
Tom Hopson

2. Schematic of the 1-10day discharge forecasting sequence for the Brahmaputra and Ganges rivers (which was fully-automated in 2004).
Boxes with circles done using CRON. Describe CRON next and how to download NASA TRMM data.

3. Automatic (background) Job Processing: CRON
Cron is a time-base job scheduler in Unix-like computer operating systems. 'cron' is short for 'chronograph’. Cron enables users to schedule jobs (commands or shell scripts) to run automatically at a certain time or date. It is commonly used to perform system maintenance or administration, though its general purpose nature means that it can be used for other purposes, such as connecting to the Internet and downloading .

4. Note: you may need to specify full paths of programs since SHELL
Crontab file:
minute (0 - 59)
| hour (0 - 23)
| | day of month (1 - 31)
| | | month (1 - 12) OR jan,feb,mar,apr ...
| | | | day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat
| | | | |
* * * * * command to be executed
There are several special entries, most of which are just shortcuts,
that can be used instead of specifying the full cron entry:
Entry Description Equivalent To
@reboot Run once, at startup. None
@yearly Run once a year *
@annually (same *
@monthly Run once a month * *
@weekly Run once a week 0 0 * * 0
@daily Run once a day 0 0 * * *
@midnight (same 0 0 * * *
@hourly Run once an hour 0 * * * *
Note: you may need to specify full paths of programs since SHELL
(“dot” files) are not used by CRON

5. More on crontab file execution timing:
Some examples …

6. First steps using Linux commands:
Go to the directory
cd /home/hp/Desktop/CRONtalk

7. CRON file example:
Create a file called, say, “cron_ex”, with:
* * * * * echo "trying this out!" >> /home/hp/Desktop/CRONtalk/cron_test
Then type:
>crontab cron_ex (to install the CRON job)
>crontab -l (to see if it is working in the CRON environment
>date (to make sure a minute has passed)
After a minute in your directory, you should see a file “cron_test”
>cat cron_test (to see the output)
Then type
>crontab -r (to remove)

8. CRON IDL example:
Create a file called, say, “cron_idl”, with:
* * * * * /usr/local/bin/idl</home/hp/Desktop/CRONtalk/infile_IDL
Then create infile_IDL with:
.rnew /home/hp/Desktop/CRONtalk/testcron.pro
testcron
exit
And create testcron.pro with
PRO testcron
spawn,"echo 'trying this out!' > /home/hp/Desktop/CRONtalk/cron_test2"
openw,1,’/home/hp/Desktop/CRONtalk/cron_test3'
printf,1,'trying this out!'
close,1
end
And do as before to install … (then type >crontab -r to remove when finished)

9. CRON IDL example 2:
Now do as before with the file getRT.pro, and do as before to install …
… and you’re now downloading NASA TRMM satellite precipitation data automatically!
(then type >crontab -r to remove when finished)
Note about the “wget” command:
GNU Wget is a computer program that retrieves content from web servers, and is part of the GNU Project. Its name is derived from World Wide Web and get, connotative of its primary function. It currently supports downloading via HTTP, HTTPS, and FTP protocols, the most popular TCP/IP-based protocols used for web browsing.

11. To run the forecasting codes:
Go to the Desktop/practical
cd /home/hp/Desktop/practical
Type the following in the “practical directory”
>tar xspjSlf tarForecast.tbz2
Then go to the created Training/ directory
Modify line 20 of the program se_fcstwkarma_w2s.pro
to specify the working directory of the codes
Start up IDL, then type
>se_fcstwkarma_w2s,1 … and off it goes
When finished, look at the plots in the “scratch” directory