KaisarCode

wch.c - File and Directory Change Watcher

wch is a portable native file change notification tool. It watches files and directories for changes and emits add, upd, and del events.

Uses the native kernel API on each platform: inotify (Linux), kqueue (macOS/BSD), ReadDirectoryChangesW (Windows). No polling, no loops - the process blocks in the kernel until a change occurs.

CLI

Examples

Watch the current directory recursively:

./bin/x86_64/linux/wch .

Watch a single file (even if it doesn't exist yet):

./bin/x86_64/linux/wch ./file.txt

Output example

$ ./bin/x86_64/linux/wch /tmp/demo &
[1] 12345
$ echo "first" > /tmp/demo/a.txt
$ echo "more" >> /tmp/demo/a.txt
$ rm /tmp/demo/a.txt
add:/tmp/demo/a.txt
upd:/tmp/demo/a.txt
del:/tmp/demo/a.txt

Parameters

Output

Events are emitted one per line in type:path format:

add:/tmp/dir/newfile.txt
upd:/tmp/dir/existing.txt
del:/tmp/dir/oldfile.txt

Public API

#include "wch.h"

kc_wch_options_t opts = kc_wch_options_default();
opts.recursive = 1;

kc_wch_t *w = NULL;
kc_wch_open(&w, "/path/to/watch", &opts);

kc_wch_event_t ev;
while (kc_wch_poll(w, &ev, -1) > 0) {
    switch (ev.type) {
    case KC_WCH_ADD: /* add */ break;
    case KC_WCH_UPD: /* update */ break;
    case KC_WCH_DEL: /* delete */ break;
    }
}

kc_wch_close(w);
kc_wch_options_free(&opts);

Lifecycle

• kc_wch_open() - Opens a watcher on the given path via kc_wch_options_t. Returns KC_WCH_OK on success. If the path doesn't exist, watches the parent directory instead and filters for the target filename. Set opts.recursive for recursive directory watching.
• kc_wch_poll() - Blocks until a change event occurs. Returns 1 on event, 0 on timeout, -1 on error. The timeout_ms parameter controls blocking behavior (-1 = infinite, 0 = no wait).
• kc_wch_close() - Releases the watcher and all associated resources. Returns KC_WCH_OK. Safe to call with NULL.

Build

make clean && make

Compiled artifacts are generated under bin/{arch}/{platform}/.

Multiarch Builds

make all
make x86_64/linux
make x86_64/windows
make i686/linux
make i686/windows
make aarch64/linux
make aarch64/android
make armv7/linux
make armv7/android
make armv7hf/linux
make riscv64/linux
make powerpc64le/linux
make mips/linux
make mipsel/linux
make mips64el/linux
make s390x/linux
make loongarch64/linux

Beta Notice

This is a beta project tested only on Debian x86_64. It was created out of a personal need for these libraries, but no guarantees are provided regarding its stability or future support. You are free to test it, use it, and modify it as you please.

If you'd like to reach out, you can send an email to [email protected]. Please note that I do not accept pull requests; the goal is to avoid long-term dependency on platforms like GitHub, and I do not maintain fixed infrastructure to guarantee long-term stability for these projects.

Repo

You can download the repository and read the most up-to-date documentation directly from its official source.

GitHub: kaisarcode/wch.c

License

This project is distributed under the GNU General Public License version 3 (GPLv3).