Simple_Shell

Our Simple_Shell is an awesome entry way into the world of computers. This shell can work on any operating system or computer.

Getting Started

Prerequistes

The prerequisites to create this shell project would either be 1 year of college/High School C programing course or three months at Holberton School.

Functions

Name	Description
_strtok()	This function takes a string and seperates it into tokens by putting a null terminator where the specified delimiter is located.
_getenv
access	It is used to check if the users have permissions for the file. checks whether the calling process can access the file pathname. If pathname is a symbolic link, it is dereferenced.
free	This function frees up the memory that was allocated for the string, array or integer, etc.
del_newline	This function overwrites a newline character before the null character in a string. This is being used with get_line
_strdup	Copies and allocates memory for a sting. returns a pointer to malloc'd space containing the copy of the string.
_strcmp	Custom built function that compares two strings.
_strlen	Custom built function that returns the length of a string
path_combo	This function combines two strings with a / symbol in between them. After, they have been combined and malloced, it is returns a pointer.
env_path_parse	This function parses the pathline from the environment variable. After the memory is allocated for the array of strings, it returns the environment variable line.
free_if_needed	This function frees the allocated memory of a pointer if it is not null.
free_array	This function frees the string in a pointer array.
get_path	This function returns the absolute path to a command.
built_ins_abs_paths_check	Checks the initial command.
executer	This function was build to make sure that execve kills any child process. Travis decided to put exit(187) as a safety measure.
_putchar	This function allows you to print a character to standard out(stdout).
print_prompt	This function prints the command line prompt.
print_string	This lets you print a string ended with a null terminator.
_atoi	This function helps convert a string to an integer.
colon_check	checks a string for leading, appending, or back to back colons. Return -1 if no leading, ending, or double colons are present. Otherwise, it returns the corresponding index where the colon appears.

Error message

Name	Description
perror_permission	prints the permission denied error message. This is being used in switch cases.
perror_file	prints the no such file or directory error message. used in a switch case.
perror_command	prints the command not found error message. used in a switch case.
perror_string	prints a string to the standard error.

Built-ins

Name	Description
ptr_array_print	This built-in prints an array of strings. the array of string contain the variables. This returns the number of strings printed.
exit_status	Exits the program with specific exit statys and frees the allocated memory.

System call

Name	Description
execve	Executes a program referered to by pathname. it is used to kill process.
fork	It is an operation where a process id is cloned.
Wait	This system call wait for a process to change status. When a process is forked, it will create a clone or a child process id. if wait is in the original(parent process id), it will wait for the child process id is completed/killed before it continues on.

Switch cases

Name	Output
case 0	perror_command(av[0], com_path);
case 1	perror_permission(com_path, av[0]);
case 2	perror_command(av[0], com_path);
case 3	executer(com_path, flags);
case 4	ptr_array_print(env);
case 5	exit_status(com_path, flags, av[0]);

Compilation

With the command below, this will be used to compile our shell

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

Running the tests

$ ./hsh
($) /bin/ls
hsh main.c shell.c
($)
($) exit
$

Flowchart

Contributing

Authors

Travis Bearden and Kenneth Fernandez.