My Shell

This project is a custom shell implementation in C. The shell supports basic command execution, directory traversal, process management, and more. The source files are organized in the codes directory.

Features

• Custom Commands: Implemented custom commands like hop, reveal, log, seek, proclore,alias,activities,ping,fg,bg,neonate,iMan
• Directory Traversal: Easily navigate directories with custom commands.
• Process Management: Manage processes with custom and built-in commands.
• Signal Handling: Handles signals to manage processes and cleanup resources.
• Colored Output: Outputs file and directory names in colored text for easier identification.

Files and Directories

• main.c: The main entry point for the shell program.
• split.c: Utility functions for string splitting and command parsing.
• log.c: Handles logging and history management.
• process.c: Manages processes and signal handling.
• hop.c: Implements the hop command for directory traversal.
• reveal.c: Implements the reveal command for listing files and directories.
• proclore.c: Implements process-related commands.
• seek.c: Implements the seek command for file and directory search.
• alias.c: Implements the alias command for creating and managing aliases.
• activities.c: Implements the activities command for displaying recent commands.
• ping.c: Implements the ping command for network connectivity testing.
• fg.c: Implements the fg command for foreground process management.
• bg.c: Implements the bg command for background process management.
• neonate.c: Implements the neonate command for process printing periodically.
• iMan.c: Implements the iMan function for printing man pages from internet using sockets.

Limitations and Assumptions

The shell implementation makes certain assumptions and has specific limitations based on defined constants:

• Maximum Sizes:

  • MAX_SIZE = 4097: Maximum size for buffers used to store paths, usernames, system names, etc.
  • max_comm_size = 100: Maximum number of commands that can be handled at once.
  • BUFFER_SIZE = 1024: Buffer size for input and output operations.
  • concatenated_commands[256 * 100]: Buffer for storing concatenated commands.
  • log_path[MAX_SIZE]: Buffer for storing the log file path.

• Commands with '&' and '|' consecutively will not work.

• Tokenising is done first with '|' and then with '&'.

• Aliases are stored in log files.

• Aliases have to be written with a space before and after =.

• If 'sleep 100' entered and sent to background and stopped. And if fg is called for it(using its pid) then it will run for less than 100 secs.

• Double quotes function will not work in execvp.

• If there are two | one after another with no spaces then the command till '||' will run and command in right of '||' will be ignored. But if two | have space between them then it is invalid command.

• If theres | in the start or end it is invalid command.

• If command is 'wc < a.txt > b.txt > new.txt' then wc will read from a.txt and print it in b.txt. Basically wc will take input or give output to file after first >(>> also) or <.

• Logging:

  • no_of_logs = 15: Maximum number of logs stored in memory.
  • commands_logged = 0: Counter for the number of commands logged during a session.

• Background Processes:

  • MAX_BG_PROCESSES = 1024: Maximum number of background processes that the shell can track simultaneously.
  • bg_process_count = 0: Counter for tracking the current number of background processes.

• Memory Allocation:

  • Dynamically allocates memory for background flags using malloc. The implementation assumes successful memory allocation without errors.

• Foreground Process Time Tracking:

  • The shell only tracks and adds to the total time slice for foreground processes whose time slice exceeds 2 seconds. However, it prints the total time that all foreground processes have accumulated.

• Signal Handling:

  • Utilizes struct sigaction and handles signals using the SA_RESTART and SA_NOCLDSTOP flags.

• Libraries:

  • The shell relies on standard C libraries like unistd.h, signal.h, stdlib.h, stdio.h, and custom header files like split.h.

Compilation

To compile the project, run the following command in the root directory:

make

After compilation, you can run the shell using
make run

Alternatively, you can directly run the executable
./a.out

To remove the compiled files and the executable, run
make clean