🖥️ Custom Shell README 📜

Table of Contents

• Introduction
• Basic System Calls
  • Display Requirement
  • Input Requirements
  • warp Command
  • peek Command
  • pastevents Command
  • System Commands
  • proclore Command
  • seek Command
• Processes, Files, and Misc.
  • I/O Redirection
  • Pipes
  • Redirection along with Pipes
  • activities Command
  • Signals
  • fg and bg Commands
  • neonate Command
• Networking
  • iMan Command

Introduction

This document describes the implementation and usage of a custom shell with various features such as system calls, file handling, process management, and networking.

Basic System Calls 📞

Display Requirement

The shell prompt displays in the form <Username@SystemName:~>. The username and system name are dynamically retrieved, and the current directory is shown relative to the shell's home directory (~).

Input Requirements

• The shell supports a list of commands separated by ; or &.
• Commands can be executed in the background with &.
• Multiple commands can be given using ;.
• Commands with errors will display an error message.

warp Command 🚀

The warp command changes the current working directory.

• Supports ., .., ~ (home directory), and - (previous directory).
• Executes sequentially if multiple arguments are provided.
• Prints the full path after changing the directory.

peek Command 👀

The peek command lists files and directories.

• Default behavior excludes hidden files.
• Flags:
  • -l: Displays extra information.
  • -a: Includes hidden files.
• Supports symbols like ., .., ~, and -.

pastevents Command 🕰️

The pastevents command is similar to the history command in Bash.

• Stores the 15 most recent commands.
• Commands identical to the previous one are not stored.
• Persistent over different shell runs.
• Subcommands:
  • pastevents: Displays the history.
  • pastevents purge: Clears the history.
  • pastevents execute <index>: Executes a command from the history.

System Commands 💻

• Executes other system commands present in Bash (e.g., emacs, gedit).
• Supports both foreground and background processes.
• Prints the time taken for processes running more than 2 seconds.

proclore Command 📊

The proclore command displays process information.

• Displays:
  • PID
  • Process status (R/R+/S/S+/Z)
  • Process group
  • Virtual memory
  • Executable path

seek Command 🔍

The seek command searches for files or directories.

• Flags:
  • -d: Only look for directories.
  • -f: Only look for files.
  • -e: Prints content or changes the directory if only one match is found.
• Supports symbols like ., .., ~, and -.
• Prints "No match found!" if no match is found.
• Prints "Invalid flags!" if both -d and -f are used simultaneously.

Processes, Files, and Misc. 📁

I/O Redirection 🔀

• Supports >, >>, and <.
• Creates or appends to files as necessary.
• Displays "No such input file found!" if the input file does not exist.

Pipes ⛓️

• Supports piping between commands.
• Executes commands sequentially from left to right.
• Displays "Invalid use of pipe" if improperly used.

Redirection along with Pipes 🔄

• Supports I/O redirection with pipes.
• Ensures proper functionality when used together.

activities Command 📋

The activities command lists all running processes spawned by the shell.

• Displays:
  • Command name
  • PID
  • State (Running or Stopped)

Signals 🚦

• ping <pid> <signal_number>: Sends a signal to a process.
• Handles special keyboard inputs:
  • Ctrl-C: Sends SIGINT to foreground process.
  • Ctrl-D: Logs out of the shell.
  • Ctrl-Z: Stops the foreground process.

fg and bg Commands 🌟

• fg <pid>: Brings a background process to the foreground.
• bg <pid>: Changes the state of a stopped background process to running.

neonate Command 👶

• neonate -n [time_arg]: Prints the PID of the most recently created process every [time_arg] seconds until x is pressed.

Networking 🌐

iMan Command ℹ️

• iMan <command_name>: Fetches and displays the man page for a given command from the internet.