SIMPLE SHELL

This shell is a command-line interpreter that provides a command line user interface for Unix-like operating systems.
It is both an interactive command language and a scripting language, and is used by the operating system to control the execution of the system using shell scripts.

Users type commands which get executed within the session.

Example:

$pwd - to print working directory                                               
$cd .. - to change direcory to previous directory                               
$echo - to print to standard output                                             
$cat - to read a file's content

Below are the files in this repository and a description of the code they contain

main.c

Contains the main code of the shell where all the rest of the other functions are used to make the shell run.

Makes the Shell run continously and also listens for signals when a user presses ctrl + c

Returns 0 on success and 1 when something goes wrong as the shell runs

signal.c

Contains a function that listens for when a user presses ctrl + c and prevents the shell session from closing.

It prints a new line and clears the standard output instead of interrupting the running shell

Prototype: void sigint_handler(int sig)

readline.c

Contains the function readline() that gets the user input from standard input

Prototype: char *readline(void);

Returns:

The pointer to the string of input the user gave if successfull

NULL if it fails

splitline.c

Contains the function splitline(char *line) that tokenises the user input and stores the resulting tokens in an array

Prototype: char **splitline(char *line)

Returns:

The array of tokens if succesful

NULL on failure

execute.c

Contains the function execute(char **args) and it's where the actual linux commands are executed.

Prototype: int execute(char **args);

It also uses a few other functions.

Return:

1 on success

0 on failure

getpath.c

Contains the function get_path(char *command) that gets the full path of given command from the PATH variable

Prototype: char *get_path(char *command);

Returns:

A pointer to the full path of the command on success

NULL on failure

`_getenv.c`

Contains the function _getenv(char *name) that finds the environment variable requested by user

Prototype: char *_getenv(char *var);

Returns:

The value of the environment variable on success

NULL on failure

tokenize_env.c

Contains the function tokenize_env(char *path) that tokenizes the PATH to return a list of folders

Prototype: char **tokenize_env(char *path);

Returns:

An array of directories on success

NULL on failure

Custom Commands

Some custom commands for the shell

`_printenv.c`

Contains the function _printenv(void) that pints all the environment variables

Prototype: void _printenv(void);

It is called by typing the command env in the shell

Helper Functions

These are some of the helper functions used across most of the core functions.

Most of these are also availabe in the standard library but we were supposed to write the functions ourselves

`_putchar.c`

Contains the functions _putchar(char c) that writes a character c to stdout

Prototype: int _putchar(char c);

Return:

1 on success

-1 on error

`_strcat.c`

Contains the function _strcat(char *dest, char *src) that concatonates two strings passed to it

Prototype: char *_strcat(char *dest, char *src);

Returns:

A pointer to the new string

`_strcmp.c`

Contains the function _strcmp(char *s1, char *s2) that compares two strings

Prototype: int _strcmp(char *s1, char *s2);

Returns:

0 if equal

negative value if less than

positive if greater than

`_strlen.c`

Contains the function _strlen(char *s) that finds the length of string

Prototype: int _strlen(char *s);

Returns:

Length of the string passed on success

`_strncmp.c`

Contains the function _strncmp(char *str1, char *str2, int n) that compares n bytes in str1 and str2

Prototype: int _strncmp(char *str1, char *str2, int n);

Returns:

0 if str2 is less than str1

< 0 if str1 < str2,

0 is str1 is equal to str2

man file

man_1_simple_shell

This is the man file for the shell

Usage: man ./man_1_simple_shell

haeder file

shell.h

Contains all the function prototypes and header files used in this project.

muindetuva/simple_shell