SIMPLE SHELL

INTRODUCTION

Kernel

• It's the heart of the operating system.
• Interact with the hardware.
• Management of the memory, task scheduling and file management.

Simple Shell

• The simple_shell its a command interpretet that communicate with the operating system.
• Translates commands typed and convert it into a computer lenguage.
• Interface between a user and the operating system.

Commands and Utilities

• Several commands as ls, pwd, cd, etc that come along with some options.

Files and Directories

• Files organized into directories.

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OBJECTIVES

• Display a prompt and wait for the user to type a command. A command line always ends with a new line.
• The prompt is displayed again each time a command has been executed.
• The command lines are simple, no semicolons, no pipes, no redirections or any other advanced features.
• The command lines are made only of one word. No arguments will be passed to programs.
• If an executable cannot be found, print an error message and display the prompt again.
• You have to handle the “end of file” condition (Ctrl+D)
• handle special characters : ", ', `, , *, &, #.
• Implement the exit built-in, that exits the shell.
• Implement the env built-in, that prints the current environment.

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INSTALL

clone

-First of all, you should clone the repository of simple_shell from this link.

• Clone

Compilation

• Once you have the files of the simple_shell you must compile it with GCC.
• gcc -Wall -Werror -Wextra -pedantic *.c -o hsh

Execute

• Finally to execute the simple_shell you must to use "./hsh".
• ./hsh

FUNCTIONS.

FUNCTION	FILE	DESCRIPTION
- main	- bigshell.c	- 'Entry point of the program.'
- checkinfo	- checkstr.c	- 'Check the information enter by the user and look for commands'
- new_command	- checkstr.c	- 'Create a duplicate process for the new command'
- maintoken	- checkstr.c	- 'Work with token functions allowing access in different parts of code'
- divtokens	- checkstr.c	- 'Split the string in an array of tokens'
- numtoken	- checkstr.c	- 'Counts tokens in the passed string.'
- lookpath	- directory.c	- 'looks for the path of the program'
- lookenvpath	- directory.c	- 'Look for environmental variable'
- divpath	- directory.c	- 'Split the path string as array of path directories'
- lookdir	- directory.c	- 'Check in directories of pathtokens for the command'
- strpath	- directory.c	- 'Join path directory string with command string'
- changedir	- inc_funct.c	- 'Change CWD to the parameter in cd, no parameter change HOME'
- varenv	- inc_funct.c	- 'Print environment variables'
- free_exit	- inc_funct.c	- 'Exit after free allocated resources'
- intfunct_exe	- inc_funct.c	- 'Lookup for function needed to execute'
- intfunct	- inc_funct.c	- 'Lookup for builtin functions'
- wrtnum	- aux_funct.c	- 'Write a number'
- _strdup	- aux_funct.c	- 'Copy a string'
- printfun	- aux_funct.c	- 'Print string by character'
- _put_char	- aux_funct.c	- 'Writes a character to stdout'
- _strcmp	- aux_funct.c	- 'Compare two strings'
- freestr	- aux_funct1.c	- 'Free pointers to a string'
- freeptr	- aux_funct1.c	- 'Free double pointer variables'
- wrterrex	- aux_funct1.c	- 'Write exec errors'
- wrterror	- aux_funct1.c	- 'Write message error when command is not found'
- _strlen	- aux_funct1.c	- 'Function that return the lenght of a string'

USAGE examples:

synopsis example:

• ls [OPTION]... [FILE]...

• pwd [OPTION]...

• cat [OPTION]... [FILE]...

System call:

• The Syscall is the way in wich a computer request a service from the kernel, of the operating system.

PROCESS CONTROL

SYSCALL	DESCRIPTION
- exit()	- 'terminates the calling process "immediately"'
- fork()	- 'Create a process '
- wait()	- 'Wait for a single object '

MANIPULATION

SYSCALL	DESCRIPTION
- read()	- 'Read a file'
- write()	- 'Write a file '
- close()	- 'Close handle '

OTHERS

SYSCALL	DESCRIPTION
- chdir()	- 'Changes the current working directory to that specified in path.'
- execve()	- 'Executes the program pointed to by filename'
- signal()	- 'System call installs a new signal handler for the signal with number signum '
- getpit()	- 'Get the current process id '
- stat()	- 'These functions return information about a file.'

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BLOG LINK

Medium:

• What happens when you type ls -l in the shell.

• Article

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MAN-PAGE.

MAN OPTION	DESCRIPTION
./man_1_simple_shell	Simple_shell is a command lenguage interpreter that execute commands read from the standar input or from a file .

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FLOW CHART.

AUTHORS.

• Alexander Urrego - mateo-a - @mateo_a
• Sergio Quiroga - sergioq7777 - @SergioQ32400329