codeyenum / simple_shell

simple_shell Table of Contents

Description
File Structure
Requirements
Installation
Example of Use
Authors

Description

Shell is often confused with as a terminal window and I was a victim of this false thinking too. I got to find out that a shell is just a middleman between the typed commands entered by the users and the computer system that performs an action based on the commands(command line interpreter). The first Unix shell was written by Ken Thompson in 1971. The picture below best describes the shell.

Image of Shell

This project deals with creating a shell with minimal functionalities and the standard functions that were employed were:- access, execve, exit, fork, free, fstat, getline, malloc, perror, signal, stat, wait, write. File Structure

AUTHORS - This file lists the people that contributed the project
man_1_simple_shell - Custom manual page for the simple shell.
shell.h - This is the header file that contains the library dependencies and structures required for compilation of the program.
builtins.c - Contains the major builtin functions. Down below lists the functions names and their use:
    check_for_builtins - This helps to check if the command is a builtin
    new_exit - This exits the shell with an option for specified status
    _env - This prints the environment shell variables to stdout.
    new_setenv - initializes a new environment variable, or modifies an existing one
    new_unsetenv - removes an environment variable
builtins2.c - helper functions for the builtins
    add_key - creates a new environment variable
    find_key - finds an environment variable in the environment array
    add_value - creates a new environment variable string
    _atoi - converts a string into a non-negative integer
environment.c - These are functions that deals with the environment.
    make_env - creates the shell's environment from the parent process
    free_env - frees the shell's environment
errors.c - functions related to printing errors
    print_error - prints an error message to the standard error
    _puts2 - prints a string to the standard error
memory_allocation.c - Functions related to memory allocation
    _realloc - a custom realloc function for arrays of pointers
new_strtok.c - Custom strtok and helper functions
    check_match - checks if a character matches any in a string
    new_strtok - a custom strtok for the shell
path.c - functions related to executing commands
    path_execute - executes a command in the PATH
    find_path - finds the PATH environment variable
    check_for_path - checks if the command is in the PATH
    execute_cwd - executes a command with an absolute path
    check_for_dir - checks if the command contains an absolute path
simple_shell.c - These is the main shell functions for the shell
    main - the main function of the program
    sig_handler - handles SIGINT( this is what is sent when ^C is sent as a command by the user)
strfunc.c - Functions concerned with manipulating the string
    _puts.c - This writes to the standard output.
    _strdup - duplicates a string
    _strcmpr - compares two strings
    _strcat - concatenates two strings with a / in the middle
    _strlen - calculates the length of a string
tokenize.c
    tokenize - creates an array of tokens from a buffer with a specified delimiter

Requirements

simple_shell should be compiled on Ubuntu 20.04 LTS using gcc, using the options -Wall -Werror -Wextra -pedantic -std=gnu89. Installation

Clone this repository.
Change directories into the repository: cd simple_shell
Compile: gcc -Wall -Werror -Wextra -pedantic *.c -o hsh
Run the shell in interactive mode: ./hsh
Or run the shell in non-interactive mode: example echo "pwd" | ./hsh

Example of Use

$ ./hsh $ # This is our rendition of the shell $ ls -al total 100 drwxrwxr-x 3 vagrant vagrant 4096 May 18 20:23 . drwxr-xr-x 9 vagrant vagrant 4096 May 18 17:41 .. drwxrwxr-x 8 vagrant vagrant 4096 May 18 20:23 .git -rw-rw-r-- 1 vagrant vagrant 146 May 18 16:14 AUTHORS -rw-rw-r-- 1 vagrant vagrant 5522 May 18 20:22 README.md -rw-rw-r-- 1 vagrant vagrant 2863 May 18 16:14 builtins.c -rw-rw-r-- 1 vagrant vagrant 2391 May 18 16:14 builtins2.c -rw-rw-r-- 1 vagrant vagrant 710 May 18 16:14 environment.c -rw-rw-r-- 1 vagrant vagrant 1217 May 18 16:14 errors.c -rwxrwxr-x 1 vagrant vagrant 26984 May 18 20:23 hsh -rw-rw-r-- 1 vagrant vagrant 2512 May 18 16:14 man_1_simple_shell -rw-rw-r-- 1 vagrant vagrant 485 May 18 16:25 memory_allocation.c -rw-rw-r-- 1 vagrant vagrant 1276 May 18 16:29 new_strtok.c -rw-rw-r-- 1 vagrant vagrant 3432 May 18 16:30 path.c -rw-rw-r-- 1 vagrant vagrant 1821 May 18 16:31 shell.h -rw-rw-r-- 1 vagrant vagrant 1510 May 18 16:33 simple_shell.c -rw-rw-r-- 1 vagrant vagrant 2116 May 18 17:12 strfunc.c -rw-rw-r-- 1 vagrant vagrant 720 May 18 17:13 tokenize.c

Authors

Abanum Oliseyenum

Nnadi Chigozie