Programming Perl, 4th Edition

ioctl

ioctl FILEHANDLE, FUNCTION, SCALAR

This function implements the ioctl(2) syscall, which controls I/O. To get the correct function definitions, first you’ll probably have to say:

require "sys/ioctl.ph";     # perhaps /usr/local/lib/perl/sys/ioctl.ph

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. (The Perl distribution includes a script called h2ph to help you do this, but running it is nontrivial.) SCALAR will be read or written (or both) depending on the FUNCTION—a pointer to the string value of SCALAR will be passed as the third argument of the actual ioctl(2) call. If SCALAR has no string value but does have a numeric value, that value will be passed directly rather than a pointer to the string value. The pack and unpack functions are useful for manipulating the values of structures used by ioctl. If the ioctl needs to write data into your SCALAR, it is up to you to ensure that the ...