pSOSystem System Calls - Read

pHILE+ System Calls get_fn
Usage
Hex Mnemonic Description
0x200E E_FORD Directory file expected.
0x2025 E_IDN Illegal device name.
0x2050 E_BADNFS NFS volume; illegal operation.
One usage of get_fn() is to get the current directory. In the example below, the
current directory’s FN is returned in dir_fn.
unsigned long dir_fn; /*current directory */
if (get_fn(“.”, &dir_fn) != 0) {
}
/*Insert some error processing here */;
The pseudocode below shows how to get the current directory’s full pathname,
rather than just the FN.
1. Get the directory’s FN in dir_fn with get_fn(“.”) as above.
2. Open the parent directory (“..”) with open_dir().
3. Search the parent directory for the directory entry of the current directory.
a. Read a directory entry with read_dir().
b. Compare the directory entry’s d_filno with the FN of the current directory.
c. Repeat steps a and b until they match.
d. Remember the matching directory entry’s d_name. It is the last component
of the current directory’s pathname.
4. Close the open directory with close_dir().
5. Repeat steps 1-4 for the parent directory of the current directory, the
grandparent of the current directory, etc., until reaching the root directory. The
root directory is reached when either get_fn() of the parent directory is an
error, or get_fn() of the parent directory is the same as get_fn() of the
directory.
pSOSystem System Calls 2-47
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