Boot Option Handling
Mac OS X provides a simple parse routine, PE_parse_boot_arg, for basic boot argument passing. It supports both flags and numerical value assignment. For obtaining values, you write code similar to the following:
unsigned int argval; |
|
if (PE_parse_boot_arg("argflag", &argval)) { |
/* check for reasonable value */ |
if (argval < 10 || argval > 37) |
argval = 37; |
} else { |
/* use default value */ |
argval = 37; |
} |
Since PE_parse_boot_arg returns a nonzero value if the flag exists, you can check for the presence of a flag by using a flag that starts with a dash (-) and ignoring the value stored in argvalue.
The PE_parse_boot_arg function can also be used to get a string argument. To do this, you must pass in the address of an array of type char as the second argument. The behavior of PE_parse_boot_arg is undefined if a string is passed in for a numeric variable or vice versa. Its behavior is also undefined if a string exceeds the storage space allocated. Be sure to allow enough space for the largest reasonable string including a null delimiter. No attempt is made at bounds checking, since an overflow is generally a fatal error and should reasonably prevent booting.
