Re: Call a command from C on as400

[Scott Klement <klemscot@xxxxxxxxxxxx>]

This probably belongs on C400-L, but real quick...

   spawn() starts a batch job that you can communicate with via pipes
       or sockets.  Since it's a batch job, it cannot run interactive
       commands like DSPUSRPRF.  And since it requires all of the
       overhead of creating a new job, it's not an efficient way to run
       commands.

   spawn() would be appropriate for running a QShell command or script
       since in the unix-like environment, it's common to use descriptors
       for stdin,stdout,stderr to send/get results and errors from
       commands. This is NOT the way that stuff is done in normal
       OS/400 commands like DSPUSRPRF, however.

   spawnp() is like spawn(), except that your PATH envvar is observed.
      Though, again, that won't help you with things like DSPUSRPRF.
      It will help you with unix-like utilities such as grep and find.

   system() can be used to run native OS/400 commands in your current
      job.  Assuming that your current job is an interactive one, you
      do things like DSPUSRPRF.

   Example:

   #include <stdio.h>
   #include <stdlib.h>
   #include <stddef.h>

   int main(int argc, char **argv) {

      if (system("DSPUSRPRF USRPRF(QSYSOPR)") != 0) {
          fprintf(stderr, "DSPUSRPRF command failed with %s\n",
             _EXCP_MSGID);
          exit(255);
      }

      return 0;
   }

But, as I said, this is off-topic for MIDRANGE-L and David will probably
complain that it should be on C400-L.


On Mon, 24 May 2004, Walt Fles wrote:

> All,
> Im trying to use spawn to call a command without having to specify a
> complete path, ie
> without having to say "/qsys.lib/mylib.lib/mypgm.pgm"
> Is there something I have to set up in my environment?
>
> also, how do I call from within C commands such as "dspusrprf", or do a:
> "call pgm(mylib/mypgm)" from within C.  I've already did a
> putenv("PATH=%LIB%")
> but that does not seem to help.
>
> I am using WDS5722 on V5R2.