simple_watcher

Overview

simple_watcher provides SCOOP-compatible file system change monitoring for Eiffel applications. It wraps the Win32 ReadDirectoryChangesW API through a clean C interface, enabling real-time detection of file system changes without threading complications.

The library monitors directories for file additions, deletions, modifications, and renames, with configurable watch flags for filtering specific change types. Supports both single-directory and recursive subdirectory monitoring.

Part of the simple_* ecosystem of focused, single-purpose Eiffel libraries.

Quick Start

Installation

<library name="simple_watcher" location="$SIMPLE_EIFFEL/simple_watcher/simple_watcher.ecf"/>

Watch a Directory

local
    watcher: SIMPLE_WATCHER
    event: detachable SIMPLE_WATCH_EVENT
do
    -- Create watcher for a directory
    create watcher.make ("C:\MyFolder", False, {SIMPLE_WATCHER}.Watch_all)

    if watcher.is_valid then
        watcher.start

        from until not watcher.is_watching
        loop
            -- Poll for changes (non-blocking)
            event := watcher.poll

            if attached event as e then
                print ("Event: " + e.event_type_string + " - " + e.filename + "%N")
            end

            sleep (100)  -- Small delay to avoid busy-waiting
        end

        watcher.close
    end
end

Recursive Monitoring

local
    watcher: SIMPLE_WATCHER
do
    -- Watch directory and all subdirectories
    create watcher.make ("C:\MyFolder", True, {SIMPLE_WATCHER}.Watch_all)

    if watcher.is_valid then
        watcher.start
        -- ... monitoring loop ...
        watcher.close
    end
end

Features

File Changes

Detect file additions, deletions, modifications

Rename Tracking

Track file and directory rename operations

Recursive Mode

Optional monitoring of subdirectories

Non-Blocking

Poll for events without blocking

Watch Flags

Flag	Value	Description
`Watch_file_name`	0x0001	File creation/deletion/rename
`Watch_dir_name`	0x0002	Directory creation/deletion/rename
`Watch_attributes`	0x0004	Attribute changes
`Watch_size`	0x0008	File size changes
`Watch_last_write`	0x0010	Last write time changes
`Watch_security`	0x0020	Security descriptor changes
`Watch_all`	0x003F	All of the above

Event Types

Type	Code	Description
Added	1	File/directory created
Removed	2	File/directory deleted
Modified	3	File/directory modified
Renamed	4	File/directory renamed

API Reference

Feature	Description
`make (path, recursive, flags)`	Create watcher for directory
`start`	Begin watching for changes
`poll`	Poll for next event (non-blocking)
`wait`	Wait for next event (blocking)
`close`	Stop watching and release resources
`is_valid`	Is the watcher properly initialized?
`is_watching`	Is the watcher actively monitoring?

SIMPLE_WATCH_EVENT

Feature	Description
`event_type`	Type of change (1-4)
`filename`	Name of affected file/directory
`is_added`	Was a file/directory created?
`is_removed`	Was a file/directory deleted?
`is_modified`	Was a file/directory modified?
`is_renamed`	Was a file/directory renamed?
`event_type_string`	Human-readable event type