SQLRPGLE Shorts – How to Call QCMDEXC with IBM i SQL
Surely every RPG programmer is familiar with the QCMDEXC *API for exciting any IBM i Command from within any HLL (High Level Language) program.
What is QCMDEXC?
The Execute Command (QCMDEXC) API runs a single command. It is used to run a command from within a high-level language (HLL) program or from within a CL program where it is not known at compile time what command is to be run or what parameters are to be used.
QCMDEXC is called from within your HLL program, and the command it runs is passed to it as a parameter on the CALL command.
After the command runs, control returns to your HLL program.
Of course, those really crusty old gray haired programmers will remember the System38 version of the same *API called QCAEXEC 😉
Let’s say we wanted to WRKSPLF with spool files from an RPG program
In good old-fashioned RPG, from the AS400 and iSeries days of the 1980’s and 1990’s, we had good old column based RPG code. You would most likely see an example something like this:
** ** define variable for command and another variable containing the length of it ** C MOVE 'WRKSPLF' CMDSTR 7 C Z-ADD 7 CMDLEN 155 ** ** now pass that WRKSPLF command into the QCMDEXC API ** C CALL 'QCMDEXC' C PARM CMDSTR C PARM CMDLEN 155
For the last 20+ years, since the advent of freeformat RPG C-specs only, it is the same code looks like this
// declare a procedure called 'execute' to call QCMDEXC d Execute PR ExtPgm('QCMDEXC') d CmdStr 20 0 Options(VarSize) const d CmdLen 15 5 Const // declare a variable to contain the command to be executed d CMDSTR S 200 // now pass that WRKSPLF command into the QCMDEXC API c eval CMDSTR = 'WRKSPLF' c callp Execute(CMDSTR:%len(CMDSTR))
For the last 10+ years with fully freeformat RPG the common coding technique might look like this:
// declare a procedure called 'execute' to call QCMDEXC dcl-pr Execute extpgm('QCMDEXC'); *n char(32000) const options(*varsize); *n packed(15: 5) const; end-pr; // declare a variable to contain the command to be executed dcl-s CMDSTR char(200); // now pass that WRKSPLF command into the QCMDEXC API CMDSTR='WRKSPLF'; Execute(CMDSTR:%len(CMDSTR));
But now with SQLRPGLE we have an easier way of the doing the same thing:
// Simply tell SQL to run out command exec sql call qsys2.qcmdexc('WRKSPLF');
I tend to use the SQLRPGLE technique more often than not.
We can add some error handling using SQL Return codes, or you could add a big monitor group to handle errors:
// Simply tell SQL to run out command monitor; exec sql call qsys2.qcmdexc('WRKSPLF'); on-error; // add some error handling for a failed execution of command endmon;