ZDIR(3)

🎀 NAME 🎀

zdir — the class for working with file-system directories, bestie 💖

(also hi yes this is ZDIR(3) out of the CZMQ Manual, and it's a two-parter because apparently we're doing a whole saga today 🦋)

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✨ SYNOPSIS ✨

Okay so first things first, queen: this class is stable, and it's staying that way unless something is literally an emergency:

//  This is a stable class, and may not change except for emergencies. It
//  is provided in stable builds.

🌸 making and unmaking a dir 🌸

//  Create a new directory item that loads in the full tree of the specified
//  path, optionally located under some parent path. If parent is "-", then
//  loads only the top-level directory, and does not use parent as a path.
CZMQ_EXPORT zdir_t *
    zdir_new (const char *path, const char *parent);

So you hand it a path and it slurps up the whole tree, and you can also tuck it under some parent. But plot twist: if parent is literally "-", it only loads the top-level directory and does not use parent as a path. iykyk 💅

//  Destroy a directory tree and all children it contains.
CZMQ_EXPORT void
    zdir_destroy (zdir_t **self_p);

This one takes the entire tree and every child in it out. No survivors, it's giving apocalypse 😭

🔍 getters, the little info girlies 🔍

//  Return directory path
CZMQ_EXPORT const char *
    zdir_path (zdir_t *self);

Gives you the directory path back. Slay.

//  Return last modification time for directory.
CZMQ_EXPORT time_t
    zdir_modified (zdir_t *self);

The last time this directory was touched. Iconic behaviour honestly.

//  Return total hierarchy size, in bytes of data contained in all files
//  in the directory tree.
CZMQ_EXPORT off_t
    zdir_cursize (zdir_t *self);

Total hierarchy size, in bytes, of every file in the whole tree. Big number energy ✨

//  Return directory count
CZMQ_EXPORT size_t
    zdir_count (zdir_t *self);

How many dirs. That's it. That's the function. 🎀

📋 the list one (read the warning, bestie) 📋

//  Returns a sorted list of zfile objects; Each entry in the list is a pointer
//  to a zfile_t item already allocated in the zdir tree. Do not destroy the
//  original zdir tree until you are done with this list.
//  Caller owns return value and must destroy it when done.
CZMQ_EXPORT zlist_t *
    zdir_list (zdir_t *self);

⚠️ ATTENTION BESTIE ⚠️ Every entry in that list is a pointer to a zfile_t that's already allocated inside the zdir tree. So do not destroy the original zdir tree until you're fully done with this list. Also: caller owns the return value and must destroy it when done. Both rules. No skipping. 🫶

🗑️ removal hours 🗑️

//  Remove directory, optionally including all files that it contains, at
//  all levels. If force is false, will only remove the directory if empty.
//  If force is true, will remove all files and all subdirectories.
CZMQ_EXPORT void
    zdir_remove (zdir_t *self, bool force);

Vibe check on force:

• force is false → it only removes the directory if it's empty (so polite, so demure 🌸)
• force is true → it removes all files and all subdirectories, at all levels. Full send 💀

🪞 diff / resync 🪞

//  Calculate differences between two versions of a directory tree.
//  Returns a list of zdir_patch_t patches. Either older or newer may
//  be null, indicating the directory is empty/absent. If alias is set,
//  generates virtual filename (minus path, plus alias).
//  Caller owns return value and must destroy it when done.
CZMQ_EXPORT zlist_t *
    zdir_diff (zdir_t *older, zdir_t *newer, const char *alias);

Diffs two versions of a tree and hands you a list of zdir_patch_t patches. Either older or newer can be null — that just means the directory is empty/absent, no drama. And if alias is set, it generates a virtual filename (minus path, plus alias). Caller owns the return value and must destroy it when done — you know the drill by now 👑

//  Return full contents of directory as a zdir_patch list.
//  Caller owns return value and must destroy it when done.
CZMQ_EXPORT zlist_t *
    zdir_resync (zdir_t *self, const char *alias);

Same deal but it's the full contents of the directory, as a zdir_patch list. Caller owns it, destroy it when done. 💜

🧠 cache, fprint, print 🧠

//  Load directory cache; returns a hash table containing the SHA-1 digests
//  of every file in the tree. The cache is saved between runs in .cache.
//  Caller owns return value and must destroy it when done.
CZMQ_EXPORT zhash_t *
    zdir_cache (zdir_t *self);

Loads the directory cache and gives you a hash table with the SHA-1 digests of every file in the tree. The cache gets saved between runs in .cache. And yes — caller owns the return value and must destroy it when done. 🍓

//  Print contents of directory to open stream
CZMQ_EXPORT void
    zdir_fprint (zdir_t *self, FILE *file, int indent);

Prints the contents to an open stream file, with indent.

//  Print contents of directory to stdout
CZMQ_EXPORT void
    zdir_print (zdir_t *self, int indent);

Same but straight to stdout. Main character energy 🌈

👀 zdir_watch, the whole little tutorial 👀

Okay this one comes with its own mini-manual and we are keeping all of it, no cap:

//  Create a new zdir_watch actor instance:
//
//      zactor_t *watch = zactor_new (zdir_watch, NULL);
//
//  Destroy zdir_watch instance:
//
//      zactor_destroy (&watch);
//
//  Enable verbose logging of commands and activity:
//
//      zstr_send (watch, "VERBOSE");
//
//  Subscribe to changes to a directory path:
//
//      zsock_send (watch, "ss", "SUBSCRIBE", "directory_path");
//
//  Unsubscribe from changes to a directory path:
//
//      zsock_send (watch, "ss", "UNSUBSCRIBE", "directory_path");
//
//  Receive directory changes:
//      zsock_recv (watch, "sp", &path, &patches);
//
//      // Delete the received data.
//      free (path);
//      zlist_destroy (&patches);
CZMQ_EXPORT void
    zdir_watch (zsock_t *pipe, void *unused);

So: zactor_new (zdir_watch, NULL) to spin it up ✨, zactor_destroy (&watch) to take it down, zstr_send (watch, "VERBOSE") if you want verbose logging of commands and activity, then SUBSCRIBE / UNSUBSCRIBE with a directory_path, and zsock_recv (watch, "sp", &path, &patches) to catch the changes. And don't forget to clean up: free (path); and zlist_destroy (&patches); — free your data, bestie, that's the rule 🧚

🧪 the self test 🧪

//  Self test of this class.
CZMQ_EXPORT void
    zdir_test (bool verbose);

Tests itself. Pass verbose. Self-care honestly 💅

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note note note: Please add '@interface' section in './../src/zdir.c'.

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🦋 DESCRIPTION 🦋

So what does zdir actually do, you ask? It gives you access to the file system index. It loads a directory tree — that's a directory plus all its child directories — into a zdir structure, and then lets you navigate that structure. 🫶

And the why? It exists mainly to wrap non-portable OS functions to do this. That's the whole reason it's here. Periodt. 👑

also, a little to-do someone left us: Please add @discuss section in ./../src/zdir.c.

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okay but that's genuinely not the end, part 2 is literally right there, keep scrolling bestie 🌈💖

🎬 EXAMPLE 💖

okay bestie, this is the whole entire example, straight from the zdir_test method. it's giving "look at everything this API can do" and honestly? it ate. don't panic — it's just one long test function, and every single line is below, untouched, exactly as it lives. read it like a story: set up the paths, nuke the leftovers from old aborted tests, make a file, diff two dirs, then sit and watch a directory like it's your fave reality show. 🍓

const char *SELFTEST_DIR_RW = "src/selftest-rw";

const char *testbasedir  = "zdir-test-dir";
const char *testfile1 = "initial_file";
const char *testfile2 = "test_abc";
char *basedirpath = NULL;   // subdir in a test, under SELFTEST_DIR_RW
char *filepath1 = NULL;      // pathname to testfile in a test, in dirpath
char *filepath2 = NULL;      // pathname to testfile in a test, in dirpath

basedirpath = zsys_sprintf ("%s/%s", SELFTEST_DIR_RW, testbasedir);
assert (basedirpath);
filepath1 = zsys_sprintf ("%s/%s", basedirpath, testfile1);
assert (filepath1);
filepath2 = zsys_sprintf ("%s/%s", basedirpath, testfile2);
assert (filepath2);

/*
char *relfilepath2 = NULL;      // pathname to testfile in a test, in dirpath
relfilepath2 = zsys_sprintf ("%s/%s", testbasedir, testfile2);
assert (relfilepath2);
*/

// Make sure old aborted tests do not hinder us
zdir_t *dir = zdir_new (basedirpath, NULL);
if (dir) {
    zdir_remove (dir, true);
    zdir_destroy (&dir);
}
zsys_file_delete (filepath1);
zsys_file_delete (filepath2);
zsys_dir_delete  (basedirpath);

dir = zdir_new ("does-not-exist", NULL);
if (dir) {
    zdir_remove (dir, true);
    zdir_destroy (&dir);
}

// need to create a file in the test directory we're watching
// in order to ensure the directory exists
zfile_t *initfile = zfile_new (basedirpath, testfile1);
assert (initfile);
zfile_output (initfile);
fprintf (zfile_handle (initfile), "initial file\n");
zfile_close (initfile);
zfile_destroy (&initfile);

zdir_t *older = zdir_new (basedirpath, NULL);
assert (older);
if (verbose) {
    printf ("\n");
    zdir_dump (older, 0);
}
zdir_t *newer = zdir_new (SELFTEST_DIR_RW, NULL);
assert (newer);
zlist_t *patches = zdir_diff (older, newer, "/");
assert (patches);
while (zlist_size (patches)) {
    zdir_patch_t *patch = (zdir_patch_t *) zlist_pop (patches);
    zdir_patch_destroy (&patch);
}
zlist_destroy (&patches);
zdir_destroy (&older);
zdir_destroy (&newer);

zdir_t *nosuch = zdir_new ("does-not-exist", NULL);
assert (nosuch == NULL);

// zdir_watch test:
zactor_t *watch = zactor_new (zdir_watch, NULL);
assert (watch);

int synced;
if (verbose) {
    zsock_send (watch, "s", "VERBOSE");
    synced = zsock_wait(watch);
    assert ( synced == 0);
}

// wait for initial file to become 'stable'
#ifdef CZMQ_BUILD_DRAFT_API
zclock_sleep ((int)zsys_file_stable_age_msec() + 50);
#else
zclock_sleep (5050);
#endif

zsock_send (watch, "si", "TIMEOUT", 100);
synced = zsock_wait(watch);
assert (synced == 0);

zsock_send (watch, "ss", "SUBSCRIBE", basedirpath);
synced = zsock_wait(watch);
assert(synced == 0);

zsock_send (watch, "ss", "UNSUBSCRIBE", basedirpath);
synced = zsock_wait(watch);
assert(synced == 0);

zsock_send (watch, "ss", "SUBSCRIBE", basedirpath);
synced = zsock_wait(watch);
assert(synced == 0);

zfile_t *newfile = zfile_new (basedirpath, testfile2);
zfile_output (newfile);
fprintf (zfile_handle (newfile), "test file\n");
zfile_close (newfile);

zpoller_t *watch_poll = zpoller_new (watch, NULL);

// poll for a certain timeout before giving up and failing the test
void* polled = NULL;
#ifdef CZMQ_BUILD_DRAFT_API
polled = zpoller_wait(watch_poll, (int)zsys_file_stable_age_msec() + 150);
#else
polled = zpoller_wait(watch_poll, 5150);
#endif
assert (polled == watch);

// wait for notification of the file being added
char *path;
int rc = zsock_recv (watch, "sp", &path, &patches);
assert (rc == 0);

assert (streq (path, basedirpath));
freen (path);

if (verbose)
    zsys_debug("zdir_test() : added : zlist_size (patches)=%d",
        zlist_size (patches) );
assert (zlist_size (patches) == 1);

zdir_patch_t *patch = (zdir_patch_t *) zlist_pop (patches);
if (verbose)
    zsys_debug("zdir_test() : added : zdir_patch_path (patch)='%s'",
        zdir_patch_path (patch) );
assert (streq (zdir_patch_path (patch), basedirpath));

zfile_t *patch_file = zdir_patch_file (patch);
if (verbose)
    zsys_debug("zdir_test() : added : zfile_filename (patch_file, \"\")='%s'",
        zfile_filename (patch_file, "") );
assert (streq (zfile_filename (patch_file, ""), filepath2));

zdir_patch_destroy (&patch);
zlist_destroy (&patches);

// remove the file
zfile_remove (newfile);
zfile_destroy (&newfile);

// poll for a certain timeout before giving up and failing the test.
#ifdef CZMQ_BUILD_DRAFT_API
polled = zpoller_wait(watch_poll, (int)zsys_file_stable_age_msec() + 150);
#else
polled = zpoller_wait(watch_poll, 5150);
#endif
assert (polled == watch);

// wait for notification of the file being removed
rc = zsock_recv (watch, "sp", &path, &patches);
assert (rc == 0);

assert (streq (path, basedirpath));
freen (path);

if (verbose)
    zsys_debug("zdir_test() : removed : zlist_size (patches)=%d",
        zlist_size (patches) );
assert (zlist_size (patches) == 1);

patch = (zdir_patch_t *) zlist_pop (patches);
if (verbose)
    zsys_debug("zdir_test() : removed : zdir_patch_path (patch)='%s'",
        zdir_patch_path (patch) );
assert (streq (zdir_patch_path (patch), basedirpath));

patch_file = zdir_patch_file (patch);
if (verbose)
    zsys_debug("zdir_test() : removed : zfile_filename (patch_file, \"\")='%s'",
        zfile_filename (patch_file, "") );
assert (streq (zfile_filename (patch_file, ""), filepath2));

zdir_patch_destroy (&patch);
zlist_destroy (&patches);

zpoller_destroy (&watch_poll);
zactor_destroy (&watch);

// clean up by removing the test directory.
dir = zdir_new (basedirpath, NULL);
assert (dir);
zdir_remove (dir, true);
zdir_destroy (&dir);

zstr_free (&basedirpath);
zstr_free (&filepath1);
zstr_free (&filepath2);

#if defined (__WINDOWS__)
zsys_shutdown();
#endif

the way that this test cleans up after itself first, before it even starts testing? that's the self-care we deserve. 💅 notice zdir_new ("does-not-exist", NULL) twice — once to prove it handles a real leftover dir, and once to assert you get NULL back for a path that genuinely isn't there (assert (nosuch == NULL)). also yes, the zdir_watch bit subscribes, unsubscribes, and subscribes again, because we check things. and on __WINDOWS__ it calls zsys_shutdown(); on the way out. icon behavior. ✨

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👑 AUTHORS 🌈

the czmq manual was written by the authors in the AUTHORS file. they're the real ones, no cap.

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🦋 RESOURCES 💜

Main web site:

report bugs to the email zeromq-dev@lists.zeromq.org[1]

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📜 COPYRIGHT 🎀

Copyright (c) the Contributors as noted in the AUTHORS file. This file is part of CZMQ, the high-level C binding for 0MQ: http://czmq.zeromq.org. This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/. LICENSE included with the czmq distribution.

so basically: it's MPL v. 2.0, and if the license file wasn't shipped with your copy, that URL is where you get it. read it, bestie. 📖

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🗒️ NOTES 🌸

1. zeromq-dev@lists.zeromq.org mailto:zeromq-dev@lists.zeromq.org

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and that's a wrap on ZDIR(3) 💖 this page came from CZMQ 4.2.1, dated 01/16/2026, and yeah — it's the ZDIR(3) manual page, slay. go build something iconic with it. periodt. 🫶✨