Learn some seldom-known yet practical techniques to utilize User Space Objects.
Before I read the post Re: *Usrspc question by Simon Coulter in
- Using User Space APIs in the
- User Space APIs in the
- Space Management and Space Addressing MI instructions
Work with *USRSPC Objects via the DSPF and EDTF Commands
The Display File (DSPF) and Edit File (EDTF) commands allow users to display or change the content of either a stream file or a member of a database file. (Note that the EDTF command works only with source physical files or data physical files that are not externally described.) As mentioned, they can also be used to display or change the content of a *USRSPC object. When data stored in a *USRSPC object is in text format, it's pretty handy to be able to display or change the content of the *USRSPC via the DSPF and EDFT commands.
To edit the character content of a *USRSPC object, you can issue an EDTF command against the *USRSPC object and set the Stream file (STMF) parameter to the IFS path name of the *USRSPC—for example, EDTF STMF('/qsys.lib/lsbin.lib/spc
To browse the data content of a *USRSPC object, you can issue a DSPF command and specify the IFS path name of the *USRSPC object as the STMF parameter of the DSPF command—for example, DSPF STMF('/qsys.lib/lsbin.lib/spc
Note that if the data content of a *USRSPC object contains newline characters (*CR, *LF, *CRLF, *LFCR), DSPF or EDTF separates lines according the newline characters in the data content. If the data content of a *USRSPC object does not contain any newline characters, DSPF and EDTF will adopt an arbitrary record length of 80 and 75, respectively; in other words, DSPF/EDTF displays each 80-character/75-character as one line.
Work with *USRSPC Object from Within a Shell Environment
A *USRSPC object can be used as the source of an input redirection or the target of an output redirection. For example, the following shell command issued in a QShell or PASE shell session will redirect both the standard output and the standard error generated by the list of shell commands to *USRSPC object QGPL/SPC
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> ( echo STDOUT; ls no-such-thing ) > /qsys.lib/qgpl.lib/spc $ |
Note that the output redirection will create the target *USRSPC object if it doesn't already exist or cause the existing *USRSPC object to be extended or truncated to proper size. Also, the appending redirection operator >> cannot be used on a *USRSPC object.
The sort command in the following example redirects the standard input to *USRSPC object QGPL/SPC
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> cat > /qsys.lib/qgpl.lib/spc > > Jack > > Anny > > David > > eof $ > sort -k 1 < /qsys.lib/qgpl.lib/spc Anny David Jack $ |
Note that QShell and PASE shell use different character encoding (EBCDIC and PC character encoding, respectively), so you should not use the data content stored in a *USRSPC object by QShell as the input of a PASE shell command or program, and vice versa.
Besides input/output redirection, a *USRSPC object can also be used as the source or destination argument of the file operation command cp. For example, the following PASE shell commands copy PASE program echo into the associated space of *USRSPC QGPL/SPC0B and then copy the content of QGPL/SPC0B to a new PASE program shout.
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> cp /QOpenSys/QIBM/ProdData/OS400/PASE/bin/echo \ > > /qsys.lib/lsbin.lib/spc14.usrspc $ > ./shout "I'm back :p" I'm back :p $ |
Exchange Information with Shell Programs via *USRSPC Objects in a Native HLL Program
The QShell utilities and the PASE shell utilities are necessary for managing Integrated File System (IFS) objects. They are also helpful for developers and operators to work with /QSYS.LIB objects from the CL environment or programs written in native High Level Languages (HLL)—for example, you can use a QShell (or PASE shell) <I>find command to look up source members by name, file type, last access time, etc. However, for IBM i HLL programs, it's still inconvenient to exchange information with shell commands or programs—for example, receiving the output of a shell command. One possible solution is to store information to be shared with shell commands or programs in *USRSPC objects.
Imagine that you are expected to collect all source members with a specific library that have been modified within a week and write the source member names to a database file or a spooled file. To achieve your goal, you may follow these steps:
- Run a QShell find command to list the source members that satisfy the search criteria (being modified within a week), and redirect the output of your find command to a *USRSPC object (say, MYGPL/ONEWEEK). The QShell find command might look like this: find /qsys.lib/mysrclib.lib -type f -ctime -7 > /qsys.lib/mygpl.lib/oneweek.usrspc.
- Read the search result stored in MYGPL/ONEWEEK in an RPG program, parse the character lines, and write them to a database file or a spooled file.
The following example CL program spc01.clp and RPG program spc02.rpgle demonstrate the above shown steps.
SPC01
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/** @file spc01.clp */ /** Calls: SPC02 */ PGM PARM(&SRCLIB &GPL) DCL VAR(&SRCLIB) TYPE(*CHAR) LEN(10) DCL VAR(&GPL) TYPE(*CHAR) LEN(10) DCL VAR(&FINDCMD) TYPE(*CHAR) LEN(80) DCL VAR(&SPCNAM) TYPE(*CHAR) LEN(20) CHGVAR VAR(&FINDCMD) VALUE('find /qsys.lib/' *CAT + &SRCLIB *TCAT '.lib -type f -ctime -7 > + /qsys.lib/' *CAT &GPL *TCAT + '.lib/oneweek.usrspc') STRQSH CMD(&FINDCMD) /* Run QShell find command */ CHGVAR VAR(&SPCNAM) VALUE('ONEWEEK ' *CAT &GPL) CALL PGM(SPC02) PARM(&SPCNAM) /* Parse the output + of previous issued QShell find command */ DSPSPLF FILE(QSYSPRT) JOB(*) SPLNBR(*LAST) /* Show + search result */ |
SPC02
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h dftactgrp(*no) fQSYSPRT o f 132 printer * SYSBIF memchr() /copy mih-comp
d qual_name_t ds qualified d obj d lib
* My prototype d i_main pr extpgm('SPC02') d spc_name likeds(qual_name_t)
* Materialize space size d matspsz pr 10i 0
* Prototype of the Retrieve Pointer to User Space API d qusptrus pr extpgm('QUSPTRUS') d spc_name likeds(qual_name_t) d @spp *
d @spp s * d c s d spsz s 10i 0 d disp s 10i 0 d ln s * Newline character d NL c x'25' d @pos s *
d i_main pi d spc_name likeds(qual_name_t)
/free // Retrieve a space pointer addressing the *USRSPC's // associated space qusptrus(spc_name : @spp); spsz = matspsz(); // Retrieve *USRSPC size @pos = memchr(@spp : NL : spsz); // Search for NL dow @pos <> *null; disp = @pos - @spp; spsz -= disp + 1;
if disp < 132; ln = %subst(c:1:disp); else; ln = c; endif; except OREC;
// Offset @spp and search for next NL character @spp = @pos + 1; @pos = memchr(@spp : NL : spsz); enddo;
*inlr = *on; /end-free
oQSYSPRT e OREC o ln
p matspsz b * Space attribute in format SPCA0100 returned by QUSRUSAT d spca0100_t ds qualified d bytes_returned... d 10i 0 d bytes_available... d 10i 0 d spc_size 10i 0 d auto_extend d init_value d lib_name * Prototype of the Retrieve User Space Attributes API d qusrusat pr extpgm('QUSRUSAT') d attr likeds(spca0100_t) d rcv_len 10i 0 d fmt_name d spc_name likeds(qual_name_t) d ec
d attr ds likeds(spca0100_t) d rcv_len s 10i 0 inz(%size(attr)) d fmt_name s d ec s d matspsz pi 10i 0 /free qusrusat(attr : rcv_len : fmt_name : spc_name : ec); return attr.spc_size; /end-free p e |
The Retrieve Pointer to User Space (QUSPTRUS) API is used to retrieve the space pointer addressing the associated space of the target *USRSPC object, and the Retrieve User Space Attributes (QUSRUSAT) API is used to materialize the space size (the size of the associated space) of the target *USRSPC object. The Find Character Constrained (MEMCHR) system built-in is prototyped in mih-comp.rpgleinc.
Call SPC01 and specify the proper source library and result *USRSPC library parameters. The result might look like the following:
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Display Spooled File File . . . . . : QSYSPRT Page/Line 1/1 Control . . . . . Columns 1 - 78 Find . . . . . . *...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+... /qsys.lib/SRC2013.lib/A.FILE/A310.MBR /qsys.lib/SRC2013.lib/A.FILE/A311.MBR /qsys.lib/SRC2013.lib/A.FILE/A312.MBR /qsys.lib/SRC2013.lib/A.FILE/A313.MBR /qsys.lib/SRC2013.lib/A.FILE/A314.MBR /qsys.lib/SRC2013.lib/A.FILE/A316.MBR /qsys.lib/SRC2013.lib/A.FILE/A317.MBR /qsys.lib/SRC2013.lib/JAN.FILE/II301.MBR |
One More Thing
For your convenience, I'd like to mention something off topic. Suppose all you care about from a submitted QShell command is the return code. You can retrieve the return code of a QShell command via the Start QSH (STRQSH) command. You can receive the completion (*COMP) message (with message ID QSH0005) sent to the call message queue via STRQSH as shown here:
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DCL VAR(&RC) TYPE(*INT) LEN(4) STRQSH CMD('rm ~/Oh-no-no-no-no-no') RCVMSG MSGTYPE(*COMP) MSGDTA(&RC) |
The QSH#### messages are defined in message file (*MSGF) QSHELL/QZSHMSGF.
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