Calls the system call specified as the first element of the list, passing the remaining
elements as arguments to the system call. If unimplemented, produces a fatal error. The
arguments are interpreted as follows: if a given argument is numeric, the argument is passed
as an int. If not, the pointer to the string value is passed. You are responsible to make
sure a string is pre-extended long enough to receive any result that might be written into a
string. You can't use a string literal (or other read-only string) as an argument to syscall
because Perl has to assume that any string pointer might be written through. If your integer
arguments are not literals and have never been interpreted in a numeric context, you may
need to add 0 to them to force them to look like numbers. This emulates the syswrite
function (or vice versa):
require 'syscall.ph'; # may need to run h2ph
$s = "hi there\n";
syscall(&SYS_write, fileno(STDOUT), $s, length $s);
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Note that Perl supports passing of up to only 14 arguments to your system call, which in
practice should usually suffice.
Syscall returns whatever value returned by the system call it calls. If the system call
fails, syscall returns -1 and sets $! (errno). Note
that some system calls can legitimately return -1. The proper way to handle
such calls is to assign $!=0; before the call and check the value of $!
if syscall returns -1.
There's a problem with syscall(&SYS_pipe): it returns the file number of
the read end of the pipe it creates. There is no way to retrieve the file number of the
other end. You can avoid this problem by using pipe instead.
