This C program demonstrates inter-process communication and pipe handling in a UNIX environment. It creates two child processes from one parent process, using fork() and pipe(). The first child executes the ls command and the second executes the nl command, with the output of ls being piped as input to nl.

• Utilizes fork() for process creation.
• Implements pipe() for inter-process communication.
• Employs dup2() for file descriptor duplication.
• Executes external commands (ls and nl) using execvp().

This custom shell program in C offers various UNIX shell functionalities, including clearing the screen, listing directory contents, and handling directories and files. It showcases the usage of system calls and process management in a shell environment.

• Implements a basic shell interface.
• Executes commands like clear, mkdir, and chdir.
• Custom cmd_tree() and cmd_list() functions for directory manipulation and file listing.
• Utilizes stat() for file information retrieval, replicating ls -l functionality.

Each project encapsulates key concepts of operating systems, demonstrating process management, file handling, and system call usage, essential for understanding the internal workings of an OS.