Re: STRQSH monmsg in CL? -- MIDRANGE-L

Hi Frank,

Hi folks, is there a way to monitor for QSH msg's in a clp that runsinteractively?STRQSH CMD('FIND /CITIZENS/O0* >/QSYS.LIB/ZPGMR97.LIB/STDOUT.FILE/STDOUT.MBR')


There are about a million possible ways to answer this question :)

First of all, the easiest way to fix the exact symptom you've encountered,is to code it this way:


  STRQSH CMD('find /CITIZENS -name ''O0*'' >
             /QSYS.LIB/ZPGMR97.LIB/STDOUT.FILE/STDOUT.MBR')

This tells the 'find' utility to search the /CITIZENS directory, and toprint any file matching the pattern 'O0*'. If there aren't any, it'llsimply output nothing (your STDOUT.MBR will have no records in it.)

The way you coded it, you've told QShell to get a list of files stantingwith 'O0' and pass them all as separate parameters to the 'find' program.Then the find program is to read each file passed by QShell and print it.In other words, you've let QShell (rather than the 'find' program) do thesearching -- find is just echoing the names that QSHELL returned. In myversion, the 'find' utility does the work. Qshell passes it the directoryname of /CITIZENS and the 'find' utility opens up that directory andsearches for files that match the pattern.

The main benefit is that there won't be an error as long as the /CITIZENSdirectory exists.

However, that doesn't really answer your question, which was (on a moregeneral level) how to monitor for errors in a QShell program invoked froma CL program -- so I'll tackle that next:

Normally when you run a CL command from a CL program, and that commandfails, the failing command will send back an *ESCAPE message to let youknow that it failed. That's the way things work in the CPF, OS/400, i5/OSparadigm of running commands.

However, Unix doesn't have *ESCAPE messages -- again, that's an i5/OSthing, not a Unix thing. Unix programs have a different method of lettingthe caller know tha they failed. They set a return value. When thereturn value is set to 0, it means the command was successful. When it'sset to a higher number, it means it failed. Programmers are free to setthe return value to different numbers in order to distinguish differenterrors, but there's really no standard to what these numbers are, otherthan 0 means success -- and not every programmer even follows thatstandard!


Therefore if you try to do the following, it won't work:

   STRQSH CMD('find /CITIZENS/O0* > +
          /QSYS.LIB/ZPGMR97.LIB/STDOUT.FILE/STDOUT.MBR')
   MONMSG QSH0000

Tt won't work because the 'find' utility is a Unix program, and doesn'tsend back an *ESCAPE message. Therefore, there's no message to monitorfor!

Starting with V5R2, IBM added a new feature to QShell that lets QShellconvert the return status of the program into a monitorable error. WhenQShell runs the 'find' program, it checks the return value. If it's zero,QShell sends you an *ESCAPE message, thus making the unix utility worksomething like a CL program expects tit to.


To enable that feature, do this before starting QShell:

   ADDENVVAR  ENVVAR(QIBM_QSH_CMD_ESCAPE_MSG) VALUE(Y)

QShell will look for that variable. If it's set, it'll send back anescame message if the find utility returns a number other than zero. (itcan be QSH0005, QSH0006 or QSH0007)

You can use the RCVMSG command to retrieve the error message and check thestatus number, as well. For example, the following would monitor for anerror and extract the return value (also called "status code") that thefind utility has returned:


   ADDENVVAR  ENVVAR(QIBM_QSH_CMD_ESCAPE_MSG) +
              VALUE(Y) +
              REPLACE(*YES)

   STRQSH CMD('find /CITIZENS -name ''O0*'' -type f > +
          /QSYS.LIB/ZPGMR97.LIB/STDOUT.FILE/STDOUT.MBR')

   MONMSG MSGID(QSH0005) EXEC(DO)
        RCVMSG  MSGTYPE(*LAST) RMV(*YES) MSGDTA(&MSGDTA) +
                  MSGID(&MSGID)
        CHGVAR VAR(&STATUS) VALUE(%BIN(&MSGDTA 1 4))
   ENDDO

This way, no matter which error occurs, your CL program will trap it andhandle it appropriately. If you also want to suppress any output to thescreen, there's another variable for that:


   ADDENVVAR  ENVVAR(QIBM_QSH_CMD_OUTPUT) VALUE(NONE) REPLACE(*YES)

This suppresses anything displaying on the screen, which may be helpful,depending on what you're doing.

If you do not have V5R2 or later available to you, then you have to do it"the unix way" (which is more difficult to deal with from a CL program,but it's possible.)

On a Unix command-line, you can specify && to describe the name of acommand that's run when something succeeds, or || to describe the name ofa command that's run when it fails.


For example:

        ls /blah && echo "success"

This'll try to list out the "/blah" subdirectory. If it succeeds (thatis, returns a status of zero) it'll run the "echo" utility to print theword "Success".


On the other hand:

        ls /blah || echo "failed"

This is similar, but it only prints the word "failed" if the ls commanddidn't succeed (returned a status not equal to zero)

Furthermore, you can redirect output from a QShell command. In fact, youused that capability in your example code to output filenames to aphysical file member. You can also use it to suppress error messagesError messages are output to descriptor 2 rather than descriptor 1 (whichis the default) so you'd redirect them as follows:


        ls /blah 2> /dev/null

That causes error messages to be discarded (actually, it writes them to aspecial file called "/dev/null" -- /dev/null is a special file thatdiscards anything written to it.)

So on a pre-V5R2 system you could potentially detect failure and suppressoutput by doing this:


   STRQSH CMD('(find /CITIZENS -name ''/O0*'' || echo "failed" > +
          /QSYS.LIB/ZPGMR97.LIB/STDOUT.FILE/STDOUT.MBR) 2> /dev/null')

If it fails, the STDOUT member would have one record containing the word"failed". If it succeeds, it'll have zero or more pathnames that startwith /CITIZENS.

Should be easy enough to use that to determine success or failure from theCL program.


Hope that helps...