Background Tasks

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It is a common requirement to be able to schedule the running of background scripts.

Typical uses of background scripts are the loading of data from external data sources, generating and emailing HTML reports, periodic database admin, data consolidation and analysis and much more.

From Lianja 4.2 you can run background scripts written in Lianja/VFP, Python, PHP and/or JavaScript by specifying command line options to the lianjarun command.

These scripts run independently of Lianja but have full access to the Lianja Framework (GUI and non-GUI) including the Database and Recordset classes.

This provides the ability to schedule the running of scripts using cron on linux, task scheduler on windows or launchd on macOS.

Linux cron

Windows Task Scheduler

macOS launchd

You specify the input file using the -i (--input) command line switch and the output file using the -o (--output) command line switch.

You can, for example, generate an HTML report and email that to someone using the Amazon AWS Simple Email Service if you have an AWS account.

Examples:

Run a Lianja/VFP script in the current directory.

lianjarun -i myscript.dbo -o myreport.html

Run a python script in the lianjademo app.

lianjarun -i app:/lianjademo/lianjademo_pythondb.py -o myreport.html

Run a PHP script in the lianjademo app.

lianjarun -i app:/lianjademo/lianjademo_phpdb.php -o myreport.html

Run a JavaScript script in the lianjademo app.

lianjarun -i app:/lianjademo/lianjademo_javascriptdb.js -o myreport.html

Notice that these examples will access the development directories as they run lianjarun. If you want to access the runtime directories use the lianjarun command with the --runtime command line switch.

You can find a full list of command line switches here.

You can perform database admin tasks from the console or in background scripts.

The -c (--command) command line switch allows multiple commands to be concatenated into a script. Each line should be separated with a semi colon and no block statements are supported e.g if, for, do while etc.

lianjarun -c "open database southwind;select top 5 customerid,contactname,companyname \
from customers"
 CUSTOMERID CONTACTNAME                    COMPANYNAME                             
 ALFKI      Maria Anders                   Alfreds Futterkiste
 ANATR      Ana Trujillo                   Ana Trujillo Emparedado
 AROUT      Thomas Hardy                   Around the Horn again
 BERGS      Christina Berglund             Berglunds snabbkop
 BLAUS      Hannah Moos                    Bill's furniture store
5 records selected in <1ms
lianja -c "backup database southwind;"
lianja -c "optimize database southwind;"

If required you can redirect output using the -o switch.

lianjarun -c "open database southwind;select top 5 customerid,contactname,companyname \
from customers" -o mydata.txt