simple_shell is a command interpreter that uses funtions and system calls to execute programs stored in the O.S. Standard C functions and system calls employed for this simple_shell: simple_shell man page .SH NAME .B shell

• a standard command interpreter similar to the GNU Bourne-Again SHell (sh). .SH SYNOPSIS .shell .PP shell [option_name] [argument ...] .SH DESCRIPTION shell is a command programming language that executes commands read from a terminal or a file. It is the program that is running when a user logs into the system. .SH INVOCATION If no arguments are present and if the standard input of the shell is connected to a terminal, the shell is considered an interactive shell. .PP If the standard input is used with a pipeline operator, |, to connect the command, such as echo "qwerty" | ./shell, then the shell is in non-interactive mode. .SH LEXICAL STRUCTURE The shell reads input in terms of lines from a file and breaks it up into words at whitespace (blanks and tabs). .SH RETURN Upon successful return, the shell will always return a 0 for success. If the shell program fails when a command is entered incorrectly or does not exist in the $PATH, then shell program will exit out of the child process and display an error message corresponding to the error the user committed and return with a prompt. .SH BUILT-INS .PP env - When entered, shell prints the current environment to standard output. .PP exit - When entered, shell exits out of the shell program.

.SH FILES .I .sp $HOME/.profile .I .sp /etc/profile .I .sp /etc/shells .SH ALSO SEE .PP man sh, execve(2), environ .SH NOTES All files and code used in .shell were created and compiled on Ubuntu 14.04.4 LTS using GCC 4.8.4 .SH BUGS There are many features and builtin commands that are not implimented in this simple shell such as aliases, cd, and logical operators.