Mr. Robot - Holberton School 🤖

Synopsis 💭

This is a humble and simple implementation of a UNIX command line interpreter.

Description 💬

Custom version UNIX command language interpreter built as a project for Holberton School. This mini shell reads commands from either interactive mode and non-interactive mode.

Requeriments 📑

Allowed editors: vi, vim, emacs
Programs and functions will be compiled with gcc 4.8.4 using the flags -Wall -Werror -Wextra and -pedantic
All files should end with a new line
Code should use the Betty style. it will be checked using [betty-style.pl](https://github.com/holbertonschool/Betty/blob/master/betty-style\ .pl) and betty-doc.pl
No more than 5 functions per file
All your header files should be include guarded
Use system calls only when you need to
Authorized functions and system calls:
- access (man 2 access)
- chdir (man 2 chdir)
- close (man 2 close)
- closedir (man 3 closedir)
- execve (man 2 execve)
- exit (man 3 exit)
- fork (man 2 fork)
- free (man 3 free)
- stat (__xstat)(man 2 stat)
- lstat (__lxstat)(man 2 lstat)
- fstat (__fxstat)(man 2 fstat```)
- getcwd (man 3 getcwd)
- getline (man 3 getline)
- kill (man 2 kill)
- malloc (man 3 malloc)
- open (man 2 open)
- opendir (man 3 opendir)
- perror (man 3 perror)
- read (man 2 read)
- readdir (man 3 readdir)
- signal (man 2 signal)
- strtok (man 3 strtok)
- wait (man 2 wait)
- waitpid (man 2 waitpid)
- wait3 (man 2 wait3)
- wait4 (man 2 wait4)
- write (man 2 write)
- _exit (man 2 _exit)
- isatty (man 3 isatty)
- fflush (man 3 fflush)

Flowchart 📌

Below you can see all the process flow in general terms that was taken into account at the time of making the code.

Quick start 🏃

Git clone the repository:

git clone https://github.com/cbarros7/simple_shell.git

Usage 💻

All the files are to be compiled on an Ubuntu 14.04 LTS machine with:

gcc -Wall -Werror -Wextra -pedantic *.c -o hsh

Once compiled, to start the program, run: ./hsh

To exit the program, run: $ exit

The Mr. Robot supports most shell commands, such as cat, pwd, ls -la and more.

List of functions 📄

Function Name	Description
func_exit	Exit the shell.
func_printenv	Prints the current environment.
read_input	Stores whatever is passed to it as standard input.
sparse_str	Devides a string into and array of strings.
execute	Executes a command that is passed to it as the first aguement.
prompt	Prints '$' and waits for a user's input.
_getenv	Provides the value of the environment passed to it as arguement.
_which	Identifies the path of the command(*args) that is being passed.
child_process	Executes a command if the path of it is an executable file.
search_func	Search directory.
_realloc	Reallocates a space in memory.
_count_point	Memory buffer.
handle_signal	Prints new line and prompt when CTRL + C is passed as input.
_stat	Displays file or file system status.
_strstr	Locates a substring.
_strlen	Returns a string.
_strcpy	Copies a string pointed to by src to dest.
_strcat	Concatenates two strings.
_strcmp	Compare two strings.
_strdup	Copies a string to another.

Syntax 📔

Mr. Robot the user can have the experience in an interactive and non-interactive way. On the one hand, if it is invoked with a standard input that is not connected to the terminal, Mr. Robot reads and executes the received commands in order.

To use the Mr. Robot interactive mode use isatty(3). Immediately the user will see a warning $ indicating that our shell is ready to read the command.

On the other hand, in non-interactive mode the user will enter command line arguments, so Mr. Robot treats the first argument as a file from which to read the commands. In interactive mode, you can type commands from the keyboard:

Example:

$ ./hsh
$ /bin/ls

In non-interactive mode, you can pipe commands into the program using echo or cat:

Non-interactive:

Example:

$ echo "/bin/ls" | ./hsh
$ cat file_name | ./hsh

You can use the same syntax for running commands in other shells:

<command> <flags or options> <argument 1> <argument 2> ...

In non-interactive mode:

<command> | ./hsh

Built-Ins 🔨

The following built-ins are supported by the Mr. Robot:

env - Print the current environment
exit - exit program sucessfully

Return 👏

Mr. Robot returns zero indicating success and non-zero indicanting failure.

Bugs 📢

No known bugs.

Annotations 📢

We have written an article in which we deepen the internal processes within the shell by typing the command "ls -l". We talk about fundamental elements such as the PATH, and conclude with the permission structure with some examples.

Authors ✒️

Carlos Barros Github
Andrew Kalil Github

Acknowledgements 🙏

Thanks to all the software engineers, peers from different cohorts of the Holberton School, for all the learning that we have been able to acquire in this academic period culminating in this shell emulation.

For more information about Holberton, visit this link.