Simple shell

Table of Contents

• Description
• File Structure
• System and Library calls
• Installation
• Example of Use
• Authors

Description

The Simple Shell is a simple UNIX command interpreter written entirely in C. The program runs based on bash commands obtained from the command line interface (CLI) given by the user. Any text seperated by a any number of spaces, tabs or a combination of both is considered to be an argument. The respective command typed by the user is then parsed and executed as if in a regular UNIX shell.

Basic lifetime of a shell

1. Startup the shell
2. Wait for user input
3. Parse user input
4. Execute the command and return the result
5. Go back to step 2

• You could terminate the shell anytime, just type in the prompt the exit command or Ctrl-D which is interpreted as an end-of-file EOF

File structure

This table contains a brief description of the working files of the project, click on the names to get the source code.

File	Content	Description
main.h	header of the project	Contain the structure, prototypes, macros and external variable of the project.
main_loop.c	int main();	Main loop, recieve input from the Command Line Interface parse and execute it.
tokenizers.c	char **hsh_tokenizer(); char **tokenizer_path();	Split the input string into a array of tokens. Split the environment variable PATH into an array of tokens.
validators.c	char *validate_input(); int validate_spaces();	Validate if PATH exists Validate spaces, tabs and line breaks.
executors.c	int hsh_execute(); int hsh_execute_builtins();	Fork process and replace the child with a new program. Choose from an array of builtin functions.
builtin_functions.c	int hsh_cd(); int hsh_setenv(); int hsh_unsetenv(); int hsh_env(); int hsh_exit();	Change directory. Change or add and environment variable. Delete an environment variable from the environment. Print the environment variables list. Terminate the main loop and exit the shell.
helper_functions.c	void sigintH(); char *str_concat(); void *_realloc();	Handles SIGINT (CTRL + C). Concatenate two strings. Reallocate a memory block.

System and Library calls

This table lists all the System calls 2 and Library calls 3 used in this project, you could read more by clicking on their respective manual pages.

Name	Manual page	Brief description
access	man 2 access	access() function checks whether the calling process can access the file pathname. If pathname is a symbolic link, it is dereferenced.
chdir	man 2 chdir	chdir() function changes the current working directory of the calling process to the directory specified in one of its parameters.
execve	man 2 execve	execve() function allows a process to execute another program.
exit	man 3 exit	exit() function causes normal process termination.
fork	man 2 fork	fork() function creates a new process by duplicating the calling process. The new process is referred to as the child process. The calling process is referred to as the parent process.
free	man 3 free	free() function frees the memory space from the heap, which must have been returned by a previous call to malloc(), calloc(), or realloc().
getcwd	man 3 getcwd	getcwd() function copies an absolute pathname of the current working directory.
getenv	man 3 getenv	getenv() function searches the environment list to find the requested environment variable.
getline	man 3 getline	getline() function reads an entire line from input, storing the address of the buffer containing the text into a pointer.
isatty	man 3 isatty	isatty() function tests whether a file descriptor refers to a terminal.
malloc	man 3 malloc	malloc() function dynamically allocates a single large block of memory with the specified size.
perror	man 3 perror	perror() function produces a message on standard error describing the last error encountered during a call to a system or library function.
signal	man 2 signal	signal() function sets a function to handle signal i.e. a signal handler with signal number, or the address of a programmer-defined function.
strtok	man 3 strtok	strtok() function breaks a string into a sequence of zero or more nonempty tokens.
waitpid	man 2 waitpid	waitpid() function suspends execution of the calling thread until a child specified by pid argument has changed state.
fprintf	man 3 fprintf	fprintf() function sends formatted output to a stream.
setenv	man 3 setenv	setenv() function adds a variable to the environment.
unsetenv	man 3 unsetenv	unsetenv() function deletes a variable from the environment.
write	man 2 write	write() function writes to a file descriptor.

Installation

First, clone this repository to your local machine:

$ git clone https://github.com/schambig/holbertonschool-simple_shell

Then, go to the repository folder:

$ cd holbertonschool-simple_shell

Compile it with the following command:

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

Now you can run the shell in interactive mode:

$ ./hsh

Or you can run it in non-interactive mode:

$ echo "ls -la" | ./hsh

Example of Use

Interactive mode:

$ ./hsh
#(ಠ_ಠ)->$ ls
AUTHORS              executors.c         hsh     main_loop.c         README.md     validators.c
builtin_functions.c  helper_functions.c  main.h  man_1_simple_shell  tokenizers.c
#(ಠ_ಠ)->$ pwd
/root/githubRepos/holbertonschool-simple_shell
#(ಠ_ಠ)->$ exit
$

$ ./hsh
#(ಠ_ಠ)->$ ls -la
total 72
drwxr-xr-x  3 root root   232 Aug  7 23:01 .
drwxr-xr-x 14 root root  4096 Aug  8 12:22 ..
-rw-r--r--  1 root root   216 Aug  7 19:00 AUTHORS
-rw-r--r--  1 root root  4215 Aug  7 23:00 builtin_functions.c
-rw-r--r--  1 root root  2456 Aug  7 23:00 executors.c
drwxr-xr-x  8 root root   201 Aug  7 23:00 .git
-rw-r--r--  1 root root  1567 Aug  7 23:00 helper_functions.c
-rwxr-xr-x  1 root root 22744 Aug  7 23:01 hsh
-rw-r--r--  1 root root  1919 Aug  7 23:00 main.h
-rw-r--r--  1 root root  1782 Aug  7 23:00 main_loop.c
-rw-r--r--  1 root root  3703 Aug  7 18:58 man_1_simple_shell
-rw-r--r--  1 root root    29 Aug  7 18:36 README.md
-rw-r--r--  1 root root  2517 Aug  7 23:00 tokenizers.c
-rw-r--r--  1 root root  1749 Aug  7 23:00 validators.c
#(ಠ_ಠ)->$ exit
$ 

Non-interactive mode:

$ echo "env" | ./hsh
HOSTNAME=XecfXXXaXfXX
LANGUAGE=en_US:en
PWD=/root/githubRepos/holbertonschool-simple_shell
TZ=America/Los_Angeles
HOME=/root
LANG=en_US.UTF-8
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=00:su=37;41:sg=30;43:ca=30;41:
tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:
*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:
*.xz=01;31:*.zst=01;31:*.tzst=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:
*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.wim=01;31:*.swm=01;31:
*.dwm=01;31:*.esd=01;31:*.jpg=01;35:*.jpeg=01;35:*.mjpg=01;35:*.mjpeg=01;35:*.gif=01;35:*.bmp=01;35:
LESSCLOSE=/usr/bin/lesspipe %s %s
TERM=xterm
LESSOPEN=| /usr/bin/lesspipe %s
SHLVL=0
LC_ALL=en_US.UTF-8
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
OLDPWD=/root/githubRepos/holbertonschool-simple_shell-test
_=./hsh
$

Authors

Salomón Chambi	Drixner Condor	Johana Herrera

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