This function is used to inquire about the limits that apply to
the file named filename.
The parameter argument should be one of the `_PC_' constants
listed below.
The normal return value from pathconf is the value you requested.
A value of -1 is returned both if the implementation does not
impose a limit, and in case of an error. In the former case,
errno is not set, while in the latter case, errno is set
to indicate the cause of the problem. So the only way to use this
function robustly is to store 0 into errno just before
calling it.
Besides the usual file name errors (see File Name Errors),
the following error condition is defined for this function:
EINVAL- The value of parameter is invalid, or the implementation doesn't
support the parameter for the specific file.
