syscall() struct problem.

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi monks,

Im pretty new to perl, but come from a C background and am wondering is it possible to pass a struct {} address to a syscall (using the syscall() wrapper that perl provides, for example, to call nanosleep()).

I was just after a way to pause a threads execution for less than a second in a simple script, and have found myself dealving more and more into this awsome language. ;D

Looks like im hooked.

Comment on syscall() struct problem.

Replies are listed 'Best First'.
Re: syscall() struct problem. by Corion (Patriarch) on Mar 29, 2006 at 18:38 UTC
If you just want a subsecond sleep, there are two ways that don't involve `syscall()`: `use Time::Hires;` - that transforms the plain `sleep` call into a sleep call that understands fractions of seconds. Use the four argument version of `select` as `select(undef, undef, undef, 0.25);` [download] to sleep for 0.25 seconds If you're bent on using `syscall()`, the `pack` (and `unpack`) function will become your best friends, as these allow you to create binary structures and pointers to them. pack has all about it.	[reply] [d/l] [select]
Re^2: syscall() struct problem. by bart (Canon) on Mar 29, 2006 at 20:42 UTC
I'd just like to add this: The pack templates you're after are "`p`" and "`P`", which produce a pointer in a packed integer (much like "`L`"). Make sure you don't change the scalar you're pointing to between pack and syscall, or that scalar might move, and the pointer will point somewhere invalid.	[reply]