Determining Whether a User Is Already Signed On, Take Two

June 21, 2002 Timothy Prickett Morgan

Hey, Ted:

I am writing in reference to the first question and answer that was published in the May 31 “Odds and Ends” column. A reader asked the following: “Is it possible for an initial program to determine if the user who is running it is already signed on with another session?”

The technique that you described for setting an object lock is common, and it was probably adequate for the situation portrayed in the original question. However, the object-lock technique doesn’t tell you anything except ‘This object is/is not locked right now.’ Conceivably, locks can be established by users other than the one being tested. Backups might be running against the user’s library. Locks can come from many sources. This behavior could possibly even be used to bypass some level of application security.

When a more-robust solution is required, you could use the List Job (QUSLJOB) API, as illustrated in the following CL program, which I call CHKACTUSR. Pass to it the user profile name in the first parameter, and it will return the number of active jobs for that user in the second parameter:

ChkActUsr:  pgm      ( +
                        &pChkUsr      +
                        &pNbrLstE     +
                      )


   dcl   &pChkUsr       *char      10

/* Number of list entries: Listed jobs...              */

   dcl   &pNbrLstE      *dec      (7)


/*-----------------------------------------------------*/

   dcl   &usrspc     *char   10  VALUE( '#$CHKUSRAC' )
   dcl   &usrspclib  *char   10  VALUE( 'QTEMP     ' )

   dcl   &qusrspc    *char   20

   dcl   &us_hdr     *char  150   /* Space header  */

/*  The qualified search job name...                   */
   dcl   &SchJob        *char     26


   monmsg    cpf0000      exec(goto error_rtn)

/*-----------------------------------------------------*/

   chgvar  &qusrsp  ( &usrspc *cat &usrspclib )


/* Create usrspc to hold active job data from this usrprf */

   call  QUSCRTUS         ( +
                            &qusrspc              +
                            'TMPLST    '            +
                            x'00001000'             +
                            X'00'                   +
                            '*ALL      '            +
                            'Temp list usr jobs     ' +
                            '*YES      '            +
                            x'0000000000000000'     +
                          )



/*                                                     */
/*  Populate usrspc with appropriate job list data...  */
/*                                                     */

   chgvar    &SchJob      ( +
                            '*ALL      ' *cat       +
                            &pChkUsr     *cat      +
                            '*ALL      '            +
                          )

   call  QUSLJOB          ( +
                            &qusrspc               +
                            'JOBL0100'              +
                            &SchJob                +
                            '*ACTIVE   '            +
                            x'0000000000000000'     +
                            'I'                     +
                            x'00000000'             +
                            x'00000000'             +
                          )


/*  Retrieve the header data...                        */

   call  QUSRTVUS         ( +
                            &qusrspc               +
                            x'00000001'             +
                            x'00000096'             +
                            &us_hdr                +
                          )

   chgvar    &pNbrLstE     %bin( &us_hdr    133 4 )

/*------------------------------------------------------*/

Clean_up:

   dltusrspc   &usrspclib/&usrspc
   return

/*------------------------------------------------------*/
/*                                                      */
/*  Unexpected error                                    */
/*                                                      */

Error_rtn:

   chgvar      &pNbrLstE       -1
   monmsg      (cpf0000 mch0000)
   return

endpgm

— Tom Liotta, The Powertech Group, Inc.

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