Simple Shell

Synopsis

The shell project is a cumulative and comprehensive project in the Holberton curriculum. The project tests everything we have learned about the C programming language, our ability to work as a team, our skills at planning for a long term project, our talent, and grit.

Description

The Simple Shell is a simple UNIX command interpreter written entirely in C. The program runs based on bash commands obtained from the input stream by the user. Any text seperated by a single space is considered to be an argument. The respective command typed by the user is then executed as if in a UNIX shell.

To learn more about how the Shell works, here is our published article on The Startup via Medium: The Command Line with ls -l

Requirements

• Allowed editors: vi, vim, or emacs
• All files were compiled on Ubuntu 14.04 LTS
• Programs and functions were 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 is checked using betty-style.pl and betty-doc.pl
• No more than 5 functions per file
• All header files should be include guarded
• System calls are only used when needed

Compilation

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

List of Allowed Functions & System Calls

Function and/or System Call	Description
access	check real user's permissions for a file
execve	execute program
exit	cause normal process termination
fflush	flush a stream
fork	create a child process
free	free dynamic memory
getline	delimited string input
isatty	test whether a file descriptor refers to a terminal
malloc	allocate memory
perror	print a system error message
read	read from a file descriptor
strtok	extract tokens from strings
wait	wait for process to change state
write	write to a file descriptor

Usage

The shell works like this in interactive mode:

$ ./hsh
##---> /bin/ls
hsh shell.c path.c README.md

##---> ls -l
-rwxrwxr-x 1 vagrant vagrant 14136 Nov 24 21:42 hsh
-rw-rw-r-- 1 vagrant vagrant   863 Nov 24 21:42 shell.c
-rw-rw-r-- 1 vagrant vagrant   784 Nov 24 01:02 path.c
-rw-rw-r-- 1 vagrant vagrant  1449 Nov 22 23:48 README.md

##---> pwd
/home/vagrant/simple_shell

##---> exit
$

The shell works like this in non-interactive mode:

$ echo "/bin/ls" | ./hsh
hsh shell.c path.c README.md test_ls
$
$ cat test_ls
/bin/ls
/bin/ls
$
$ cat test_ls | ./hsh
hsh shell.c path.c README.md test_ls
hsh shell.c path.c README.md test_ls
$

Built-Ins

The simple shell has support for the following built-in commands:

Command	Definition
env	Prints the environment
exit	Exits the shell

The Program Flow of Our Shell

Authors

Ariana Bibiano

Erika Caoili

Robert Deprizio