🧹 SSU-Cleanupd

Overview

SSU-Cleanupd is a Linux-based automated file management program that periodically monitors user-specified directories, detects newly added files, and organizes them automatically.

This project involves developing a new shell-style command (ssu_cleanupd) using system calls, creating a daemon process, handling standard and file I/O, and implementing directory structures with linked lists. The purpose is to enhance your understanding and application of Linux system programming.

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🎯 Objectives

• Implement a custom command that behaves like a mini shell.
• Create and manage daemon processes using system calls.
• Utilize directory structures and system libraries (e.g., fcntl, scandir, realpath, exec functions, etc.).
• Practice concurrent file access synchronization via file locks.
• Improve system programming application and design skills.

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⚙️ Basic Information

• Executable name: ssu_cleanupd
• Platform: Linux
• Allowed paths: Must be subdirectories within the user’s home directory (/home/[username]/...)
• Path types: Both absolute and relative paths are supported
• Path limits:
  • Max path length: 4096 bytes
  • Max file name length: 255 bytes
• Important: system() usage is strictly prohibited (0 points if used).

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🧩 Built-in Commands

ssu_cleanupd supports the following internal commands:

Command	Description
show	Display currently running daemon processes
add	Register a new daemon process to monitor and organize a directory
modify	Modify configuration of a running daemon process
remove	Unregister (stop) a daemon process
help	Display command usage
exit	Exit the program

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💻 Usage

Command Prompt Example

When ssu_cleanupd starts, a custom prompt is displayed:

% ./ssu_cleanupd
ssu_cleanupd>

The user can input any of the following built-in commands.

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🔍 1. show

Usage:

show

Description:
Displays all currently running daemon processes and allows the user to view detailed information about each one.

Output:

• Lists daemons from /.ssu_cleanupd/current_daemon_list
• Each daemon entry displays:
  • Monitoring path
  • PID
  • Start time
  • Output directory
  • Time interval
  • Excluded paths
  • Extensions
  • Mode
  • Last 10 log entries from ssu_cleanupd.log

Example:

Current working daemon process list
0. exit
1. /home/oslab/test1/A
2. /home/oslab/test1/B
3. /home/oslab/test1/C
Select one to see process info: 1

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➕ 2. add

Usage:

add  [OPTIONS...]

Description:
Registers a daemon process that monitors `` and organizes unarranged files into an output directory.

Options

Option	Argument	Description	Default
-d	``	Set output directory path	_arranged
-i	``	Set monitoring interval (seconds)	10
-l	``	Set maximum log line count	none
-x	``	Exclude subdirectories (comma-separated)	none
-e	``	Target specific file extensions (comma-separated)	all
-m	``	Set duplicate handling mode (1–3)	1

Mode Reference

Mode	Behavior
1	Move the newest file if duplicates exist
2	Move the oldest file if duplicates exist
3	Do not move duplicates

Files Created

File	Description
ssu_cleanupd.config	Configuration file (auto-created if not existing)
ssu_cleanupd.log	Log file with all file transfers
/.ssu_cleanupd/current_daemon_list	Daemon list file under user’s home directory

Log Format Example:

[18:00:30] [277] [/home/oslab/test2/A/1.txt] [/home/oslab/test2/A_output/txt/1.txt]

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🛠️ 3. modify

Usage:

modify  [OPTIONS...]

Description:
Modifies configuration (ssu_cleanupd.config) of a daemon currently monitoring the specified directory.

Behavior:

• Acquires a file lock before writing.
• Unspecified options remain unchanged.
• Changes take effect immediately.

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🗑️ 4. remove

Usage:

remove 

Stops and removes the daemon monitoring the given path.

Example:

ssu_cleanupd> remove test6/A

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🧭 5. help

Usage:

help

Prints descriptions of all supported commands.

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🚪 6. exit

Usage:

exit

Terminates the ssu_cleanupd program.

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🧰 Recommended System Calls and Functions

The following Linux system APIs are recommended or required for implementation:

Function	Header	Description
getopt()	``	For parsing command-line arguments
scandir()	``	For listing directory contents
realpath()	``	Convert relative paths to absolute paths
strtok()	``	String tokenization
exec*() family	``	Replace process image for daemon creation
fcntl()	``	File locking for synchronization (F_SETLKW)

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🧾 Evaluation Criteria

Component	Description	Score
ssu_cleanupd main program	Daemon shell environment	5
show command	Display daemon info	15
add command	Register and run daemon	50
modify command	Update running config	10
remove	Terminate daemon	5
help	Print command usage	5
exit	Quit the main program	5
Makefile	Proper build automation	5
Total		100 points

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🧠 Notes

• system() usage → 0 points
• Your program must manage all files under the user’s home (/home/[user]/)
• Ensure correct handling of daemon lists and file locks
• Each built-in command must correctly handle all specified exception cases
• Report must include overview, functionality, flowcharts, execution results, and commented source code

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Example Directory Structure

/home/oslab/test1/
├── A/
│   ├── ssu_cleanupd.config
│   ├── ssu_cleanupd.log
│   └── ...
├── .ssu_cleanupd/
│   └── current_daemon_list
└── ...