OS X Launch Services registry

C library, enabling programmatic access to the registry of all installed bundles and mounted disks on a system.

Usage

The launch registry contains three different type of records:

• Bundles - Applications, plugins, etc.
• Volumes - Mounted and previously mounted disks.
• Handlers - Mapping file types to applications handling them.

lsreg enables introspection of all three types.

The interface is very simplistic and iteration-based. Let's look at a really simple example:

#include "lsreg.h"

static lsreg_rec_t record;

static lsreg_rec_t *rec_factory(void *userdata) {
  return &record;
}

static int rec_handler(lsreg_rec_t *rec, void *userdata) {
  lsreg_rec_dump(rec, stdout);
  return 0;
}

int main (int argc, const char * argv[]) {
  lsreg_iterate(rec_factory, rec_handler, NULL);
  return 0;
}

This little program dumps the whole Launch Registry to stdout. Not very useful. Anyway, what happens here?

• We need to define two functions:
  • Record factory - provides each iteration with a lsreg_rec_t structure. In our example above we run everything in sequence and can thus reuse a lsreg_rec_t allocated on the stack.
  • Record handlers - called with an actual record. This is where your code does something useful (doh!).
• We call lsreg_iterate, starting iteration (the order in which records are walked is undefined).

Let's rewrite the program above to only print information about bundle records which identifier have a certain prefix, passed to the program as an command line argument.

#include <string.h>
#include "lsreg.h"

static lsreg_rec_t record;

static lsreg_rec_t *rec_factory(void *match_prefix) {
  return &record;
}

static int rec_handler(lsreg_rec_t *rec, void *match_prefix) {
  lsreg_bundle_t *bundle;
  size_t pxlen;

  if(rec->type == kLSRegRecTypeBundle) {
    bundle = (lsreg_bundle_t *)rec->rec;
    pxlen = strlen((const char *)match_prefix);
    if ( (pxlen <= strlen(bundle->identifier.name)) &&
         (strncasecmp((const char *)match_prefix, bundle->identifier.name, pxlen) == 0)
       )
    {
      puts(bundle->path);
    }
  }

  return 0;
}

int main (int argc, const char * argv[]) {
  if (argc < 2) {
    fprintf(stderr, "usage: %s PREFIX\n", argv[0]);
    return 1;
  }
  lsreg_iterate(rec_factory, rec_handler, (void *)argv[1]);
  return 0;
}

The header file lsreg.h is pretty much self-documenting.