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Simple Shell (Holberton School)

Table of Contents
  1. About Project
  2. General Workflow
  3. Installation and Usage of Program
  4. Testing
  5. Learning Objectives
  6. Files contained in this repository
  7. Credits

This project presents a minimalistic shell implementation in C, offering users a fundamental command-line interface to interact with the underlying operating system. In Linux/Unix systems, a shell serves as a crucial interface between the user and the kernel, facilitating the execution of commands and managing processes. In the context of this simple shell, it performs three primary functions: allowing users to gracefully exit the shell, displaying environment variables, and executing generic commands. The implementation leverages system calls like fork, execve, and wait for process management and employs a straightforward approach to building command paths, ensuring a basic yet functional shell experience.

General Workflow

  • Reading the Command: The shell uses the getline function to read user input and interpret the command.
  • Command Execution: The shell distinguishes between three functionalities:
  • Exit: The user can exit the shell by entering the 'exit' command.
  • Print Environment Variables: The shell supports printing environment variables using a specific command.
  • Generic Command Execution: For generic commands, the shell relies on system calls. The key system calls involved are:
    • fork: Creates a new process to execute the command.
    • execve: Loads and executes the specified command in the new process.
    • wait: Parent process waits for the child process to complete.
  • Building the Command Path: For executing generic commands, the shell builds the command path by obtaining the command from the Unix file system and appending "/cmd" to include the custom command.

Installation and Usage of Program

Prerequisites

  • C Compiler (e.g., GCC)

To use the shell, follow these steps:

  • Clone the repository:
git clone https://github.com/Ferlandoo/holbertonschool-simple_shell.git
  • Navigate to the project directory:
cd simple-shell
  • Compile the shell program:
gcc -Wall -Werror -Wextra -pedantic -std=gnu89 *.c -o hsh
  • Run the shell:
./hsh

Testing

Your shell should work like this in interactive mode:

$ ./hsh
($) /bin/ls
hsh main.c shell.c
($)
($) exit
$

But also in non-interactive mode:

$ echo "/bin/ls" | ./hsh
hsh main.c shell.c test_ls_2
$
$ cat test_ls_2
/bin/ls
/bin/ls
$
$ cat test_ls_2 | ./hsh
hsh main.c shell.c test_ls_2
hsh main.c shell.c test_ls_2
$

Learning Objectives

  • Syscalls: Understanding and implementing system calls for process creation, file I/O, and more.
  • Process: Managing processes and understanding the parent-child relationship in a Unix-like environment.
  • Environment: Handling and manipulating the environment variables.
  • Tokenization: Breaking down input commands into tokens for processing.
  • Shell Execution Flow: Understanding the flow of a basic shell program from input to command execution.

Files contained in this repository

Name Information
man_1_simple_shell Man page of the simple_shell.
main.h Header file with standard libraries and custom prototypes.
command_path.c Function that find and return full path of a command.
env-utils.c Functions that print and gets value of an environment variable.
shell.c Main function and two other functions that read and execute the commands on main.
AUTHORS Authors of this project.

Credits

Shell made by @Ferlandoo, @EderHodaj and @FloriMecaj.