Question

I’m looking for a canned C routine that does what glob(3) does, except without matching the results against filenames, e.g.

input: "x[1-4]y"
output: "x1y", "x2y", "x3y", "x4y"

regardless of whether any files with those names happen to exist. EDIT: This doesn’t need to produce the list all at once; in fact it would be better if it had an iterator-style “give me the next name now” API, as the list could be enormous.

Obviously this cannot support * and ?, but that’s fine; I only need the [a-z] notation. Support for the {foo,bar,baz} notation would be nice too.

Best option is telling me the name of a routine that is already in everybody’s C library that does this. Second best would be a pointer to a chunk of BSD-licensed (or more permissively) code. GPL code would be awkward, but I could live with it.

Answer 1

cURL (the command line tool, not the library) contains code that does this job, which is relatively easy to extract:

https://github.com/bagder/curl/blob/master/src/tool_urlglob.c
https://github.com/bagder/curl/blob/master/src/tool_urlglob.h

They’ll have to be edited to remove some dependencies on the guts of cURL that are not part of the public library interface. The API is a little confusing, so here’s some wrapper code I wrote:

#include "tool_urlglob.h"

struct url_iter
{
  char **upats;
  URLGlob *uglob;
  int nglob;
};

static inline struct url_iter
url_prep(char **upats)
{
  struct url_iter it;
  it.upats = upats;
  it.uglob = NULL;
  it.nglob = -1;
  return it;
}

static char *
url_next(struct url_iter *it)
{
  char *url;

  if (!it->uglob) {
    for (;;) {
      if (!*it->upats)
        return 0;
      if (!glob_url(&it->uglob, *it->upats, &it->nglob, stderr))
        break;
      it->upats++;
    }
  }

  if (glob_next_url(&url, it->uglob))
    abort();
  if (--it->nglob == 0) {
    glob_cleanup(it->uglob);
    it->uglob = 0;
    it->upats++;
  }
  return url;
}

Pass an array of strings to url_prep, call url_next on the result until it returns NULL. Strings returned from url_next must be deallocated with free when you’re done with them.