Implements the ioctl(2) function. You'll probably first have to say
- require "sys/ioctl.ph"; # probably in $Config{archlib}/sys/ioctl.ph
to get the correct function definitions. If sys/ioctl.ph doesn't
exist or doesn't have the correct definitions you'll have to roll your
own, based on your C header files such as <sys/ioctl.h>.
(There is a Perl script called h2ph that comes with the Perl kit that
may help you in this, but it's nontrivial.) SCALAR will be read and/or
written depending on the FUNCTION--a pointer to the string value of SCALAR
will be passed as the third argument of the actual ioctl call. (If SCALAR
has no string value but does have a numeric value, that value will be
passed rather than a pointer to the string value. To guarantee this to be
true, add a 0
to the scalar before using it.) The pack and unpack
functions may be needed to manipulate the values of structures used by
ioctl.
The return value of ioctl (and fcntl) is as follows:
- if OS returns: then Perl returns:
- -1 undefined value
- 0 string "0 but true"
- anything else that number
Thus Perl returns true on success and false on failure, yet you can still easily determine the actual value returned by the operating system:
The special string "0 but true"
is exempt from -w complaints
about improper numeric conversions.