File Name
--------------------------------------------
The Perl distribution for the AS/400 is packaged as a SAVF format file
containing a precompiled perl executable with the perl libraries.
The perl sources and libraries are a separate distribution.
The binary and libraries are stored in the file PERLPGM.SAVF;
the sources and libraries are stored in the file P500502.SAVF.
Unfortunately, the make that IBM ships as part of it's Qshell
environment does not properly implement default rules for
building things, so it cannot be used to build perl from the
sources. If you want to look at the perl sources, or attempt to
build from the sources, then skip ahead to "Downloading and
building the sources", otherwise, keep reading here for direction
on how to download and install the binaries.
The libraries are stored as separate SAVF-format files within the file
you download. Once you've restored the save file you downloaded, you
will have to restore the libraries.
Before ftping the save files onto your AS/400 system, you must
create the PERLDIST library, and the destination save file so that
ftp will store the data properly:
CRTLIB LIB(PERLDIST) TEXT('Perl 5 Distribution Library')
CRTSAVF FILE(PERLDIST/PERLPGM) TEXT('AS/400 Perl Binaries')
To restore the program files, run the following commands:
RSTOBJ OBJ(*ALL) SAVLIB(PERLDIST) DEV(*SAVF) SAVF(PERLDIST/PERLPGM)
Now, to run perl from within the Qshell environment easily, you
have to create a symbolic link using the qsh command
ln -s /qsys.lib/perldist.lib/perl.pgm /usr/bin/perl
Finally, you have to install the perl script library into the IFS
from the save file that was restored from the distribution file:
CRTDIR '/usr/local'
CRTDIR '/usr/local/lib'
RST DEV('/QSYS.LIB/PERLDIST.LIB/PERLLIB.FILE') +
OBJ('/usr/local/lib/*' *INCLUDE *SAME)
Once that's all done, you may delete the save files PERLPGM,
PERLSRC, and PERLLIB, if you wish. Make sure to read the
"Release Notes" below for any differences or limitations of
AS/400 perl.
You're now ready to program in perl.
If you are new to perl, you can find out more about it from these
books:
Gundavaram, Shishir. _CGI Programming on the World Wide Web_.
Sebastopol, CA: O'Reilly, 1996. ISBN 1-56592-168-2.
Wall, Larry, Tom Christiansen, and Randal L. Schwartz.
_Programming Perl_. 2d Ed. (Covers Perl 5). Sebastopol,
CA: O'Reilly, 1996. ISBN 1-56592-149-6.
and these web sites:
http://www.perl.org/
http://www.perl.com/perl/
Release Notes for AS/400 Perl
-----------------------------
The core perl language is fully supported on the AS/400, except
for the following issues:
- The OS/400 Unix-like APIs do not fully support file
descriptors. Perl is only supported when run from within a
Qshell environment, from the web server as a CGI processor, or
some other environment in which the POSIX file descriptors 0,
1, and 2 have been properly initialized and the environment
variable QIBM_USE_DESCRIPTOR_STDIO has been set to either 'Y'
or 'I'.
- While standard input and standard output may now be redirected
from within perl using the idiom
open(STDOUT, ">outfile")
the OS/400 runtime does not properly support closing STDOUT and
then opening it on the new file. That is, the standard perl
idiom
close(STDOUT);
out(STDOUT, ">outfile");
does not work.
- The file names "stdout", "stdin", and "stderr" are treated
specially by the OS/400 C runtime. Do NOT use these file
names within your perl programs.
- Perl scripts are not directly executable. To invoke a perl
program as a CGI, you must write a small CL program that will
dispatch to the perl script itself. For example, the script
BEGIN
CALL PGM(PERLDIST/PERL) PARM('/QOpenSys/hello.pl')
ENDPGM
will invoke the perl script 'hello.pl' in the root of the
QOpenSys file system.
There are also some issues related to the AS/400 environment that
developers porting scripts from other environments must be aware
of:
- The arguments to the perl system() function and any command
substitutions (ie. backquoted strings) must now be written as
Qshell command strings, using the limited set of Qshell
utilities that are provided.
- Perl reads scripts and data out of the integrated filesystem
(IFS). To access native OS/400 files, you must use the
IFS-style of name. For example, the file PERLDIST/QCSRC.AS400
would be written as '/QSYS.LIB/PERLDIST.LIB/QCSRC.FILE/AS400.MBR'.
See the AS/400 documentation about the IFS for details about
file naming.
- The AS/400 is an EBCDIC system. All scripts being transfered
from ASCII environments will have to be translated. FTP does
this automatically for text transfers, as does the AS/400
client access Windows file server when copying into the HFS.
- Pipes are now supported by OS/400, and perl takes advantage of
them. OS/400 does not, however, support the POSIX fork() API,
so the "|-" method of forking a new copy of your perl script
connected to the parent by a pipe is still not supported.
- AS/400 Perl supports the DBI and DB2 modules, allowing access
to databases via SQL and the perl DBI interfaces. Because
AS/400 DB2 does not have full support for converting between
numeric and character datatypes, perl programs must be more
careful about the data types they pass as parameters in SQL
statements. Integers must be declared as such, and NUMERIC and
fixed-point DECIMAL numbers must be declared as floats. See
the code in /usr/local/lib/perl5/dbsamples for examples of
using the DB2 interfaces to access the database described in
section 2.3 of "DB2 for AS/400 SQL Programming", IBM document
number SC41-5611-02.
Downloading and Building the Sources
------------------------------------
Before ftping the save files onto your AS/400 system, you must
create the PERLDIST library, and the destination save file so that
ftp will store the data properly:
CRTLIB LIB(PERLDIST) TEXT('Perl 5 Distribution Library')
CRTSAVF FILE(PERLDIST/P500502) TEXT('AS/400 Perl Sources')
To restore the sources, run the commands:
CRTDIR '/usr/local'
CRTDIR '/usr/local/src
RSTOBJ (OBJ(*ALL) SAVLIB(PERLDIST) DEV(*SAVF) SAVF(PERLDIST/P500502)
RST DEV('/QSYS.LIB/PERLDIST.LIB/PERLSRC.FILE') +
OBJ('/usr/local/src' *INCLUDE *SAME)
The libraries are stored as separate SAVF-format files within the file
you download. Once you've restored the save file you downloaded, you
will have to restore the libraries:
CRTDIR '/usr/local/lib'
RST DEV('/QSYS.LIB/PERLDIST.LIB/PERLLIB.FILE') +
OBJ('/usr/local/lib/*' *INCLUDE *SAME)
To build the sources, you need to start the Qshell environment
and run the following commands:
cd /usr/local/src/perldist
sh build.as400
The file "build.as400" is a script that invokes make several
times to build perl and the various extensions that are
supported. Unfortunately, the version of make that we used to
build perl is an IBM-internal package, so some work will be
necessary before this process will work on your system.
If you want to try to build from sources, contact
rchgo400@us.ibm.com to find out about acquiring the internal
gmake port that we used to build on the AS/400
--
David J. Fiander <davidf@mks.com>