I glanced through perlport and README.vms alike, yet remain unclear
as to how much VMS supports the myriad Unix-style IPCish syscall
facilities and related practices. Is there some other document
that describes this in better detail somewhere?
I was wondering whether VMS supports any of the following constructs,
and if so, whether there are any noteworthy variations from the
expected Unix models. (Note: Some of these are *no*great*loss* if
missing, and perhaps even a feature. :-)
0. sysopen w/ normal O_* flags, especially O_EXCL (any specials?)
1. flock() (don't semantics differ; eg, mandatory?)
2. Running command in system (or exec) and backticks
system("cmd arg1 arg2") # possible shell intervention
system("cmd", "arg1", "arg2") # unmolested execvp
$answer = `cmd args 2>&1` # snag stderr, too
$answer = `cmd args 2>/dev/null`; # discards stderr
3. Pipe open()s
open(TO_PIPE, "|cmd")
open(FROM_PIPE, "cmd|")
use IPC::Open2;
open2(FROM_PIPE, TO_PIPE, "cmd")
use IPC::Open3;
open3(TO_PIPE, FROM_PIPE, FROM_ERR, "cmd")
4. Explicit pipes
pipe(PIPE1, PIPE2)
5. Fork open()s
open(TO_MYSELF, "|-")
open(FROM_MYSELF, "-|")
6. Explicit forks
if (defined($pid = fork) { parent() }
elsif (!defined $pid) { die "fork: $!" }
else { child() }
7. Making copies of existing filehandles (&)
open(OUTCOPY, ">&STDOUT")
open(INCOPY, "<&STDIN" )
8. Making aliases through existing file descriptors (&=)
open(OUTALIAS, ">&=STDOUT")
open(INALIAS, "<&=STDIN")
open(BYNUMBER, ">&=5") # fdopen(5, "w")
9. Sockets
* Domains: Internet (AF_INET) and Unix (AF_UNIX aka AF_LOCAL)
* Protocols: TCP, UDP, raw IP, (etc?)
* socketpair for double pipes
10. Named pipes (FIFOs)
11. SysV IPC: messages, shared memory, semaphores
Also, if under VMS I print "\n" down an output pipe or socket, does
the other side get one byte or two, and if so, which? What about
reading?
thanks very much,
--tom
