TweetFollow Us on Twitter

File Path
Volume Number:7
Issue Number:9
Column Tag:TechNotes

Related Info: File Manager File Mgr (PBxxx) Standard FIle

File Path Revisited

By Alexander Colwell, Redondo Beach, CA

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

File Path Revisited

Some of the MacTutor readers probably noticed. “Hey! Somebody has already written this article before! So, why is it here again?” Well the answer is yes, it has, but only half the story. The previous MacTutor articles in January 1986 “Programming for HFS Compatibility” by Mike Schuster and in July 1986 “Make a Path Name for HFS” by Tom Taylor discuss when given the volume reference number (vRefNum) obtained by the standard SFGetFile dialog then the file’s full file path can be derived.1 But what about when given a full file path and deriving the file’s vRefNum that would be identical number returned by the SFGetFile dialog?

There are cases when applications, DA’s, or other resource codes may want to know where the file is located between invocations. In April 1990, The Apple Technical Journal’s “d e v e l o p e “ in Macintosh Q&A section recommends saving the “DirID” number that references the directory.2 This scheme is desirable because it’s simple and easy to retrieve the file’s vRefNum by calling the PBOpenWD ROM routine that can be used either by the FSOpen or PBOpen ROM routines. Another advantage is that the user can change the directory name and the directory ID number will remain the same. There are cases when this scheme fails if the directory is backed up, deleted, and restored, then the directory ID number is likely to be changed. Therefore, the application must ask you for the location of the desired file by popping up the SFGetFile dialog again.

OK. So you bother the user again by reasking the location of the file. No big deal. But what about an application managing distributed databases of files where each user has mirror copy of the files and folders relationship on its hard disk? This could be a real pain to ask the user to find hundreds of files when they periodically receive database updates, and the directories are constantly changing. This was exactly the situation I encountered a few years ago during a Macintosh application development at my place of employment.

During the development cycle of that application, I poured over the MacTutor articles and Macintosh Technical Notes on how to do this seemingly simple procedure. To my disappointment, I could not find a method that somebody else might have hacked out! After a few weeks of off and on hacking, I finally figured out how to obtain the vRefNum based on the file path that is equivalent to the same vRefNum returned by the SFGetFile dialog.

The results are two procedures rewritten from Pascal to THINK C from my old Mac programming projects. The first procedure is “GetFilePath” (rehash from previous articles) to obtain the file path given by the vRefNum. The other inverse procedure is the “GetVolRefNbr” to obtain the vRefNum given by the file path.3

The key in the “GetVolRefNbr” procedure is the use of system working directory proc ID : ‘ERIK’. This small tidbit of information can be found in Macintosh Technical Note #77. In my case, I had to figure-out the hard way how this magic working directory proc ID ‘ERIK’ was used in the SFGetFile dialog. At the time, the technical note reference about ‘ERIK’ did not exist.

The conclusion is for those who need to save the file path and then later reconstruct the vRefNum for the FSOpen or PBOpen ROM routines other than using the “DirID” method, then these procedures are for you.


1 You can find additional references in Macintosh Technical Note #238.

2 Finder’s Desktop directory/folder hierarchy. Directories and folders are analogous.

3 I use these routines in the not quite popular shareware NotePad++ desk accessory to remember the last opened “NotePad++ File”.

char *GetFilePathName(vRefNum)
 short vRefNum;              /* File's vol/dir ref    */
  WDParam      wDir;         /* Working directory     */
  HVolumeParam wVol;         /* Working HFS param blk */
  DirInfo      wCInfo;       /* Working cat info blk  */
  long         wDirID;       /* Working dir number    */
  Str255       wName;        /* Working directory name*/
  char         *wPtr;        /* Working string pointer*/
  long         wLength;      /* Working string length */
  char         *pathFileName;/* Working file path name*/

  wDir.ioNamePtr = 0L;       /* Init working directory*/
  wDir.ioVRefNum = vRefNum;
  wDir.ioWDIndex = 0;
  wDir.ioWDProcID = 0;
  wDir.ioWDVRefNum = vRefNum;

  PBGetWDInfo(&wDir,FALSE);  /* Get the directory ref */
  vRefNum = wDir.ioWDVRefNum;/* Save working vol ref #*/
  wDirID = wDir.ioWDDirID;   /* Save working dir ref #*/

  wVol.ioNamePtr = (StringPtr)&wName;/* Init vol block*/
  wVol.ioVRefNum = vRefNum;
  wVol.ioVolIndex = 0;
  wLength = 0L;              /* Set path length to zip*/
  pathFileName = NewPtr(0L); /* Set null file's path  */
  if (!PBHGetVInfo(&wVol,FALSE) &&/* Got vol info?    */
   pathFileName) {           /* Got file path pointer?*/
   if (wVol.ioVSigWord == 0x4244) {/* Check if it HFS */
    wCInfo.ioNamePtr = (StringPtr)&wName;/* Init it   */
    wCInfo.ioVRefNum = vRefNum;
    wCInfo.ioFDirIndex = -1;
    wCInfo.ioDrParID = wDirID;
    wCInfo.ioDrDirID = wDirID;

    while (wCInfo.ioDrParID != 1){/* Do full path     */
     wCInfo.ioDrDirID = wCInfo.ioDrParID;/*Move up dir*/

     if (PBGetCatInfo(&wCInfo,FALSE))/* Get dir info  */
      break;                 /* Break-out if failed!! */

     wLength += wName[0] + 1L;/* Set string length    */
     wPtr = NewPtr(wLength + 1L);/* Alloc new str     */

     if (!wPtr) {            /* Didn't get str ptr?   */
      if (pathFileName)      /* Check if got memory   */
       DisposPtr(pathFileName);/* Release it          */
      pathFileName = 0L;     /* Invalidate str pointer*/
      break;                 /* Break-out if failed!! */
                             /* Shuffle file path down*/
     BlockMove(pathFileName,wPtr + wName[0] + 1,
               wLength - (long)(wName[0]));
     DisposPtr(pathFileName);/* Release old one       */
     *(wPtr + wName[0]) = ':';/* Add dir delimeter    */
     BlockMove(&wName[1],pathFileName = wPtr, (long)(wName[0]));
   else {                    /* Oops, get vol info    */
    wLength = wName[0] + 1L; /* Set string length     */
    wPtr = NewPtr(wLength + 1L);/* Alloc new string   */

    if (wPtr) {              /* Got string pointer?   */
     *(wPtr + wName[0]) = ':';/* Tack on dir delimeter*/
     BlockMove(&wName[1],pathFileName = wPtr,

   if (pathFileName)         /* Check if got da string*/
    pathFileName[wLength] = 0;/* Set end-of-string    */
  return(pathFileName);      /* Return file path name */
short GetFilePathVolRef(pathFileName)
 char *pathFileName;         /* File's path string    */
  short        i;            /* Working index         */
  char         c;            /* Working input char    */
  short        vRefNum;      /* Working vol/dir ref   */
  WDParam      wDir;         /* Working directory     */
  HVolumeParam wVol;         /* Working HFS param blk */
  DirInfo      wCInfo;       /* Working cat info block*/
  long         wDirID;       /* Working directory ID  */
  Str255       wVolName;     /* Working volume name   */
  Str255       wName;        /* Working string name   */
  char         *wPtr;        /* Working string pointer*/
  short        wLength;      /* Working string length */
  vRefNum = 0;               /* Invalid vol/dir ref # */
  wVol.ioVRefNum = 0;        /* Init working vol ID # */
  wCInfo.ioDrDirID = 2;      /* Init top-most dir     */
  i = 0;                     /* Init working index    */
  wLength = 0;               /* Init string length    */
  c = pathFileName[i];       /* Set 1st input char    */
  while(c) {                 /* Do til get vol/dir ref*/
   if (c == ':') {           /* Check if got dir specs*/
    wName[0] = wLength - 1;  /* Set "Pascal" str len  */
    wLength = 0;             /* Reset string length   */

    if (!wVol.ioVRefNum) {   /* Check if need vol ref */
     wVol.ioNamePtr = (StringPtr)(&wVolName);

     for(wVol.ioVolIndex = 1; !PBHGetVInfo(&wVol,FALSE);
      wVol.ioVolIndex++) {
      if (EqualString(wName,wVolName,FALSE,FALSE))

     vRefNum = wVol.ioVRefNum;/* Save vol ID          */
     if (wVol.ioVSigWord != 0x4244)/* MFS ?           */
      return(vRefNum);       /* Let's get out early!  */
    else {                   /* Nope, get dir ref     */
     wCInfo.ioNamePtr = (StringPtr)(&wName);
     wCInfo.ioVRefNum = wVol.ioVRefNum;
     wCInfo.ioFDirIndex = 0;
     wCInfo.ioDrParID = wCInfo.ioDrDirID;

     if (PBGetCatInfo(&wCInfo,FALSE))/* Check dir ?   */
      return(0);             /* Nope, break-out!!!    */
   }                         /* Add to directory specs*/
   c = wName[++wLength] = pathFileName[i++];
  wDir.ioNamePtr = 0L;       /* Init dir data block   */
  wDir.ioVRefNum = wVol.ioVRefNum;
  wDir.ioWDProcID = 'ERIK';  /* Magic 'SFGetFile' ID #*/
  wDir.ioWDDirID = wCInfo.ioDrDirID;
  if (!PBOpenWD(&wDir,FALSE))/* Check if opened dir   */
   vRefNum = wDir.ioVRefNum; /* Return vol/dir ref #  */

  return(vRefNum);           /* Return vol/dir ref #  */


Community Search:
MacTech Search:

Software Updates via MacUpdate

Dash 3.4.0 - Instant search and offline...
Dash is an API documentation browser and code snippet manager. Dash helps you store snippets of code, as well as instantly search and browse documentation for almost any API you might use (for a full... Read more
AirRadar 3.1.9 - $9.95
With AirRadar, scanning for wireless networks is now easier and more personalized! It allows you to scan for open networks and tag them as favourites or filter them out. View detailed network... Read more
Printopia 2.1.22 - Share Mac printers wi...
Run Printopia on your Mac to share its printers to any capable iPhone, iPad or iPod Touch. Printopia will also add virtual printers, allowing you to save print-outs to your Mac and send to apps.... Read more
SteerMouse 5.0 - Powerful third-party mo...
SteerMouse is an advanced driver for USB and Bluetooth mice. It also supports Apple Mighty Mouse very well. SteerMouse can assign various functions to buttons that Apple's software does not allow,... Read more
Alarm Clock Pro 10.2.5 - $19.95
Alarm Clock Pro isn't just an ordinary alarm clock. Use it to wake you up in the morning, send and compose e-mails, remind you of appointments, randomize the iTunes selection, control an internet... Read more
Cocktail 10.1 - General maintenance and...
Cocktail is a general purpose utility for macOS that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more
RapidWeaver 7.1.7 - Create template-base...
RapidWeaver is a next-generation Web design application to help you easily create professional-looking Web sites in minutes. No knowledge of complex code is required, RapidWeaver will take care of... Read more
MacCleanse 5.1.6 - $29.95
MacCleanse is the product of thousands of hours of intense research and development. It meticulously scans all of the nooks and crannies of a computer for unnecessary junk that can take up huge... Read more
Slack 2.3.0 - Collaborative communicatio...
Slack is a collaborative communication app that simplifies real-time messaging, archiving, and search for modern working teams. Version 2.3.0: Note: Now requires OS X 10.8 or later New The app... Read more
Firefox 49.0.2 - Fast, safe Web browser.
Firefox offers a fast, safe Web browsing experience. Browse quickly, securely, and effortlessly. With its industry-leading features, Firefox is the choice of Web development professionals and casual... Read more

Latest Forum Discussions

See All

4 addictive clicker games like Best Fien...
Clickers are passive games that take advantage of basic human psychology to suck you in, and they're totally unashamed of that. As long as you're aware that this game has been created to take hold of your brain and leave you perfectly content to... | Read more »
Smile Inc. Guide: How not to die on the...
As if Mondays weren't bad enough, at Smile Inc. you have to deal with giant killer donuts, massive hungry staplers, and blasting zones. It's not exactly a happy, thriving work environment. In fact, you'll be lucky to survive the nine to five.... | Read more »
Oh...Sir! The Insult Simulator (Games)
Oh...Sir! The Insult Simulator 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: | Read more »
WitchSpring2 (Games)
WitchSpring2 1.27 Device: iOS Universal Category: Games Price: $3.99, Version: 1.27 (iTunes) Description: This is the story of Luna, the Moonlight Witch as she sets out into the world. This is a sequel to Witch Spring. Witch Spring 2... | Read more »
4 popular apps getting a Halloween makeo...
'Tis the season for all things spooky. So much, so, in fact, that even apps are getting into the spirt of things, dressing up in costume and spreading jack o' lanterns all about the place. These updates bring frightening new character skins, scary... | Read more »
Pokémon GO celebrates Halloween with can...
The folks behind Pokémon GO have some exciting things planned for their Halloween celebration, the first in-game event since it launched back in July. Starting October 26 and ending on November 1, trainers will be running into large numbers of... | Read more »
Best Fiends Forever Guide: How to collec...
The fiendship in Seriously's hit Best Fiends has been upgraded this time around in Best Fiends Forever. It’s a fast-paced clicker with lots of color and style--kind of reminiscent of a ‘90s animal mascot game like Crash Bandicoot. The game... | Read more »
5 apps for the budding mixologist
Creating your own cocktails is something of an art form, requiring a knack for unique tastes and devising interesting combinations. It's easy to get started right in your own kitchen, though, even if you're a complete beginner. Try using one of... | Read more »
5 mobile strategy games to try when you...
Strategy enthusiasts everywhere are celebrating the release of Civilization VI this week, and so far everyone seems pretty satisfied with the first full release in the series since 2010. The series has always been about ultra-addictive gameplay... | Read more »
Popclaire talk to us about why The Virus...
Humanity has succumbed to a virus that’s spread throughout the world. Now the dead have risen with a hunger for human flesh, and all that remain are a few survivors. One of those survivors has just called you for help. That’s the plot in POPCLAIRE’... | Read more »

Price Scanner via

Apple refurbished 2015 13-inch MacBook Airs a...
Apple has Certified Refurbished 2015 13″ MacBook Airs available starting at $759. An Apple one-year warranty is included with each MacBook, and shipping is free: - 2015 13″ 1.6GHz/4GB/128GB MacBook... Read more
64GB Apple TV on sale for $159, save $40
Best Buy has the 64GB Apple TV on sale for $40 off MSRP on their online store. Choose free shipping or free local store pickup (if available). Sale price for online orders only, in-store price may... Read more
EyeQue Introduces iOS And Android Based Advan...
Affordable vision technologies developers EyeQue have announced what they claim to be the world’s most advanced intelligent vision solution, pitched as enabling anyone, anywhere to easily and... Read more
Smartwatch Market Tanks, Declining 51.6% in 2...
The worldwide smartwatch market experienced a round of growing pains in the third quarter of 2016 (3Q16), resulting in a year-over-year decline in shipment volumes. According to data from the... Read more
CAZE announces Ultra Thin Glass Screen Protec...
Hong Kong based CAZE has announced its first ultra thin glass screen protector, the Glazz Pro for iPhone 7/7 Plus. Glazz Pro is made from chemically reinforced glass with an anti-fingerprint... Read more
11-inch MacBook Airs on sale for up to $120 o...
Newegg has 11″ MacBook Airs on sale for up to $120 off MSRP. Shipping is free: - 11″ 1.6GHz/128GB MacBook Air: $799.99 $100 off MSRP - 11″ 1.6GHz/256GB MacBook Air: $979 $120 off MSRP Read more
Up to $300 off Macs, $20 off iPads with Apple...
Purchase a new Mac or iPad using Apple’s Education Store and take up to $300 off MSRP. All teachers, students, and staff of any educational institution qualify for the discount. Shipping is free, and... Read more
Apple’s Thursday “Hello Again” Event A Largel...
KGI Securities analyst Ming-Chi Kuo, who has a strong record of Apple hardware prediction accuracy, forecasts in a new note to investors released late last week that a long-overdue redo of the... Read more
12-inch Retina MacBooks on sale for $100 off...
Amazon has 2016 12″ Apple Retina MacBooks on sale for $100 off MSRP. Shipping is free: - 12″ 1.1GHz Silver Retina MacBook: $1199.99 $100 off MSRP - 12″ 1.1GHz Gold Retina MacBook: $1199.99 $100 off... Read more
Save up to $600 with Apple refurbished Mac Pr...
Apple has Certified Refurbished Mac Pros available for up to $600 off the cost of new models. An Apple one-year warranty is included with each Mac Pro, and shipping is free. The following... Read more

Jobs Board

Security Data Analyst - *Apple* Information...
…data sources need to be collected to allow Information Security to better protect Apple employees and customers from a wide range of threats.Act as the subject Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Solutions Consultant - Apple (United...
# Apple Solutions Consultant Job Number: 52812872 Houston, Texas, United States Posted: Oct. 18, 2016 Weekly Hours: 40.00 **Job Summary** As an Apple Solutions Read more
Lead *Apple* Solutions Consultant - Apple (...
# Lead Apple Solutions Consultant Job Number: 52812906 Houston, Texas, United States Posted: Oct. 18, 2016 Weekly Hours: 40.00 **Job Summary** The Lead ASC is an Read more
*Apple* Retail - Multiple Positions- Towson,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.