At 04:12 PM 3/9/00 -0500, Charles Bailey wrote:
>Dan Sugalski <[EMAIL PROTECTED]> wrote:
>| | At 06:20 AM 3/8/00 -0700, Tom Christiansen wrote:
>| >0. sysopen w/ normal O_* flags, especially O_EXCL (any specials?)
>| | As far as I know, yep. I've certainly used it, though I don't recall
>any | VMS-special flags.
>
>Note that O_EXCL is the default under VMS Perl for all file opens; if you
>want shared access you need to ask specifically (for whcih the routines
>VMS::Stdio::vmsopen() and VMS::Stdio::vmssysopen() are provided).
Yep, true enough. The C-style access to RMS files is pretty lame, though.
We really do need to get a VMS::RMS module put together at some point.
(Yeah, I know--in what free time, exactly? :)
>| >1. flock() (don't semantics differ; eg, mandatory?)
>| | Nope. VMS has mandatory filelocking, enforced by the filesystem.
>
>flock() isn't a native part of VMS, though some emulations exist. RMS
>locking (the intrinsic stuff) is mandatory (unless you bypass it with
>raw I/O calls) and record-oriented.
That's a pretty low-level bypass, though. IIRC you have to request actual
disk blocks, which requires PHY_IO or LOG_IO privs.
>| >2. Running command in system (or exec) and backticks
>| >
>| > system("cmd arg1 arg2") # possible shell intervention
>| > system("cmd", "arg1", "arg2") # unmolested execvp
>| | Both work. Identically, as it turns out.
>
>Both go through the CLI.
With some magic munging. Trying some @ substitutions shows it works,
though, and that's got me nervous.
>| > $answer = `cmd args 2>&1` # snag stderr, too
>| > $answer = `cmd args 2>/dev/null`; # discards stderr
>| | STDERR and STDOUT are mixed together on VMS for this stuff, so the
>first is | irrelevant. The second may or may not be possible depending on
>the command, | though that particular form won't work. (It has to be
>VMSish looking, since | the system handles it)
>
>For commands sent to subprocesses, we can trap the command line and munge
>it on the way out. At the moment, we support neither construct dierctly,
>though the "2>&1" (specifically) _is_ supported when Perl is onvoked.
That's true--perl itself knows about command redirection. I like the idea
of having a command procedure interpose itself between perl and the
ultimate command and pass it stdin/out/err mailboxes so we get the full
control we don't get from lib$spawn.
>| >3. Pipe open()s
>| >
>| > open(TO_PIPE, "|cmd")
>| > open(FROM_PIPE, "cmd|")
>| >
>| > use IPC::Open2;
>| > open2(FROM_PIPE, TO_PIPE, "cmd")
>| >
>| > use IPC::Open3;
>| > open3(TO_PIPE, FROM_PIPE, FROM_ERR, "cmd")
>| | Yes, no, and no. Give me some time and open(IO_PIPE, "|foo|") will
>work, as | would open2. open3's trickier, though I just had a brilliant
>idea for a | fix. (Yes, this is a dangerous thing. :)
>
>PTYs are probably the way to go here. The up-and-coming pipe fixes will also
>help.
Keen. I may have to send Chuck the ice cream and hot fudge, then.
>| >6. Explicit forks
>| >
>| > if (defined($pid = fork) { parent() }
>| > elsif (!defined $pid) { die "fork: $!" }
>| > else { child() }
>| | No. VMS doesn't fork, though we could open things up so a fork then
>exec | works. There's support for that. (Basically some process state is
>It works currently, but with the caveat above. Basically, you're OK iff
>the only thing in the child() branch above is exec qw(some child thing).
This was why I was tempted to turn on support for fork(), but I'm still not
sure. Maybe with an explicit "use VMS::fork" or something.
>| >11. SysV IPC: messages, shared memory, semaphores
>| | Not at the moment, though we can once the VMS C RTL team gets them in.
>(We | could write our own wrapper code but, once again, nobody's done it yet)
>
>The msg* and shm* wrappers are in newer DECCRTLs, but we don't go after 'em.
>Better still would be an interface to native global sections.
I've got no msg or shm info in the headers I've got. I've been meaning to
take a look at implementing them on top of mailboxes and global sections,
but time crunches keep getting in the way.
Dan
--------------------------------------"it's like this"-------------------
Dan Sugalski even samurai
[EMAIL PROTECTED] have teddy bears and even
teddy bears get drunk
