OS X: How can I get path to Desktop directory on macOS?

Question

How can I get file path to Desktop directory as a string on macOS. I need it to be done in pure C or with some C-level framework.

Answer 1

Here's a short function, which works on more Unix based systems than just macOS and returns the current user's desktop folder:

#include <limits.h>
#include <stdlib.h>
/**
 * Returns the path to the current user's desktop.
 */
char *path2desktop(void) {
  static char real_public_path[PATH_MAX + 1] = {0};
  if (real_public_path[0])
    return real_public_path;
  strcpy(real_public_path, getenv("HOME"));
  memcpy(real_public_path + strlen(real_public_path), "/Desktop", 8);
  return real_public_path;
}

The path will only be computed once.

If the function is called more than once, the old result will be returned (not thread-safe, unless the first call was protected).

Answer 2

If you insist on using only C (why?), then your only choice is to use deprecated APIs:

#include <limits.h>
#include <CoreServices/CoreServices.h>

...

FSRef fsref;
UInt8 path[PATH_MAX];

if (FSFindFolder(kUserDomain, kDesktopFolderType, kDontCreateFolder, &fsref) == noErr &&
    FSRefMakePath(&fsref, path, sizeof(path)) == noErr)
{
    // Make use of path
}

If you need a CFURL rather than a path, you can use CFURLCreateFromFSRef() rather than FSRefMakePath().

Actually, while researching this, I found an API I hadn't known about. Apparently, you can use this, which apparently comes from Cocoa but uses only C types:

#include <limits.h>
#include <NSSystemDirectories.h>

char path[PATH_MAX];
NSSearchPathEnumerationState state = NSStartSearchPathEnumeration(NSDesktopDirectory, NSUserDomainMask);
while (state = NSGetNextSearchPathEnumeration(state, path))
{
    // Handle path
}

The form of the API is that it may return multiple results (one on each iteration of the loop), but you should get only one for the specific use here. In that case, you can change the while to and if.

Note that, with this API, returned paths for directories in the user domain may use "~" rather than the absolute path to the user's home directory. You'll have to resolve that yourself.

Answer 3

I ended with usage of Objective-C in such way:

//
//  main.m
//  search_path_for_dir
//
//  Created by Michal Ziobro on 23/09/2016.
//  Copyright © 2016 Michal Ziobro. All rights reserved.
//

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[]) {
    if(argc != 3)
        return 1;

    @autoreleasepool {
        NSArray *paths = NSSearchPathForDirectoriesInDomains(atoi(argv[1]), atoi(argv[2]), YES);
        NSString *path = [paths objectAtIndex:0];
        [path writeToFile:@"/dev/stdout" atomically:NO encoding:NSUTF8StringEncoding error:nil];
    }
    return 0;
}

And than from command line I can execute this program in that way:

./search_path_for_dir 12 1 

12 - NSDesktopDirectory

1 - NSUserDomainMask

I am using script in C that executes this program from command line and retrieves its output.

Here's C example calling this mini Cocoa App:

CFStringRef FSGetFilePath(int directory, int domainMask) {

    CFStringRef scheme = CFSTR("file:///");
    CFStringRef absolutePath = FSGetAbsolutePath(directory, domainMask);

    CFMutableStringRef filePath = CFStringCreateMutable(NULL, 0);
    if (filePath) {

        CFStringAppend(filePath, scheme);
        CFStringAppend(filePath, absolutePath);

    }

    CFRelease(scheme);
    CFRelease(absolutePath);

    return filePath;
}

CFStringRef FSGetAbsolutePath(int directory, int domainMask) {

    char path_cmd[BUF_SIZE];
    sprintf(path_cmd, "./tools/search_path_for_dir %d %d", directory, domainMask);
    char *path = exec_cmd(path_cmd);

    return CFStringCreateWithCString(kCFAllocatorDefault, path, kCFStringEncodingUTF8);
}