Using #shell and #sql in ploticus scripts


Version 2.41 Mar2009


Manual page for Using_#shell_and_#sql_in_ploticus_scripts(PL)

#shell and #sql

The #shell script directive may be used to invoke a shell command and capture the results.

The #sql script directive invokes an SQL command and captures the results. The #sql directive is currently available only for builds related to the QUISP/SHSQL package. Interfaces to other databases (MySQL, Oracle, etc.) not yet available but should be possible by coding in dbinterface.c.

Note that both of these are of limited value in ploticus... proc getdata already has a command attribute for getting data from shell command results, and it also has a sql attribute for running an SQL command. They should be viewed as providing an alternative approach.


STREAMING DATA

Here is an example of how #sql is to be used with proc getdata :
 	#proc getdata
 	delim: tab
       data:
 	#sql #dumptab select * from trialresults where trialnum = @TRIALNUM

For longer SQL commands a multi-line construct is available:

 	#proc getdata
 	delim: tab
       data:
 	#sql #dumptab 
 		select trialnum, age, sex, weight, time1, time2
 		 from trialresults 
 		where trialnum = @TRIALNUM and trialdate = @TDATE
       #endsql
The #shell directive can be used similary, but this is redundant since proc getdata already has a command attribute.


SETTING VARIABLES

These directives may be used to set variables for plot labels, etc. For example:
 	#sql #load select fullname from tsyms where tickersym = @TSYM
 
       #proc annotate
       location: min max-0.2
       text: @fullname
 

Here is an example where the results of a shell command may be used to set variables:

       // submit the command..
       #shell #processrows cat mydata | grep "^Jan"
       // get one result rows and parse out fields..
       #call $shellrow( A, B, C ) 
 
 	#proc annotate
 	location: min max-0.2
 	text: @A @B




DRIVING LOOPS

These directives may be used to drive loops that iterate once per row of results. For example:
 	// get a list of cases
 	#sql #processrows select caseid from cases
 	#while $sqlrow() = 0
 	  // get data for a case
 	  #proc getdata
 	  delim: tab
 	  data:
 	    #sql2 #dumptab select * from casedata where caseid = @caseid
 	    ... plot the case
 
 	#endloop

#shell may be used similary.


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