TCL Fork Management Library

A lightweight process management library for TCL/TclX that provides structured fork/pipe handling with an object-oriented interface.

Features

• Simple Process Creation: Easy fork management with automatic pipe setup
• Bidirectional Communication: Full duplex communication between parent and child processes
• Event-Driven Architecture: Asynchronous message handling with configurable callbacks
• Object-Oriented Interface: Clean API with configure/cget/send/destroy methods
• Namespace Isolation: Each process gets its own isolated namespace
• Flexible Callbacks: Configurable handlers for message reception, errors, and connection close

Requirements

• TCL 8.5+
• TclX extension

Installation

package require fork

Quick Start

Basic Usage

# Create a new child process
set child [::fork::newchild]

# Check if we're in parent or child
if {[$child cget whoami] eq "parent"} {
    puts "I'm the parent process"
    # Send message to child
    $child send "Hello from parent!"
} else {
    puts "I'm the child process"
    # Send message to parent
    $child send "Hello from child!"
}

Named Process Objects

# Create a child with a custom command name
set child [::fork::newchild myprocess]

# Now you can use the custom name
myprocess send "Hello world"
puts [myprocess cget whoami]

API Reference

Process Creation

::fork::newchild ?objectName?

Creates a new child process and returns a process object handle.

• objectName (optional): Custom name for the process command

Process Object Methods

send data

Sends data to the connected process (parent→child or child→parent).

$child send "Your message here"

cget option

Retrieves process information.

Options:

• whoami: Returns "parent" or "child"
• isparent: Returns 1 if parent process, 0 if child
• childpid: Returns child process ID (0 if called from child)

puts [$child cget whoami]      ;# "parent" or "child"
puts [$child cget isparent]    ;# 1 or 0
puts [$child cget childpid]    ;# Process ID or 0

configure option value ...

Configures process callbacks.

Options:

• -onget cmd: Command to execute when receiving data
• -onclose cmd: Command to execute when connection closes
• -onerror cmd: Command to execute on communication errors

$child configure -onget {puts "Received: $data"}
$child configure -onclose {puts "Connection closed"}
$child configure -onerror {puts "Communication error occurred"}

destroy

Closes communication channels and cleans up the process object.

$child destroy

Examples

Echo Server Example

package require fork

set child [::fork::newchild]

if {[$child cget whoami] eq "parent"} {
    # Parent: send messages and wait for responses
    $child configure -onget {puts "Child replied: $data"}
    $child send "ping"
    after 1000 {$child send "hello"}
    after 2000 {$child destroy; exit}
    
} else {
    # Child: echo back everything received
    $child configure -onget {
        puts "Child received: $data"
        $child send "echo: $data"
    }
}

# Keep the event loop running
vwait forever

Data Processing Pipeline

package require fork

set processor [::fork::newchild dataprocessor]

if {[$processor cget whoami] eq "parent"} {
    # Parent: send data for processing
    $processor configure -onget {puts "Processed result: $data"}
    
    foreach item {apple banana cherry date} {
        $processor send $item
    }
    
} else {
    # Child: process data and send back results
    $processor configure -onget {
        set result [string toupper $data]
        $processor send "PROCESSED: $result"
    }
}

vwait forever

Technical Details

Communication Protocol

• Uses TCL pipes for inter-process communication
• Line-buffered, non-blocking I/O
• Automatic translation handling
• Event-driven message reception using fileevent

Process Architecture

• Each child process runs in isolated namespace
• Parent maintains references to all child processes
• Automatic cleanup of file descriptors on process termination
• Support for multiple concurrent child processes

Version History

• v0.1: Initial release with basic fork/pipe management

License

This project is released under the MIT License.

Contributing

Contributions are welcome! Please feel free to submit issues and pull requests.

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Author

Created by rauleli, Apr 26, 2017