minishell

Minishell is a simple shell clone designed to teach C programming and the basics of the Linux system.

• A simplified hands-on learning experience for understanding how the shell interprets user commands, executes them, and communicates with the underlying system.

• Building a mini shell from scratch helps to understand how the shell interprets user commands, executes them, and interacts with the operating system

• Essential system-level concepts such as processes, signals, and file descriptors

[logo]

[picture of it running]

Tokenizing the command

A list of built in commands to implement

- cd : Change the current directory // can be implemented with chdir sys call

- echo : Print a message to the terminal.

- exit : Exit the shell.

- export : Set an environment variable.

- history : Display a list of previously executed commands.

- pwd : Print the current working directory.

- source : Execute commands from a file in the current shell.

- alias : Create an alias for a command.

- bg : Move a job to the background.

- fg : Move a job to the foreground.

- jobs : Display a list of active jobs.

- kill : Send a signal to a process.

- set : Set shell options and positional parameters.

- shift : Shift positional parameters to the left.

- test : Evaluate conditional expressions.

- trap : Set a command to be executed when a signal is received.

// interesting stuff to explore

#include <dirent.h> has functinos like opendir, which returns a pointer to a struct that allows traversing directories and some info about files, might work the same way as read

lstat for file info

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useful resources

Github - Sample

Blogpost Guide

Minishell Guide

Shell Program Explained Video

Currently working on

get_token.c breaks up the input command into tokens, that could be either an operator or a a word that could be either a command, file name, arguments... etc

Quoting

Is used to remove special meaning from characters or words in the shell.

• Preserve the literal meaning of an operator
• Prevent reserved keywords from being recognized as such
• Prevent parameter expansion and substitutions within here_doc????

The following characters represent themselves when quoted

|  &  ;  <  >  (  )  $  `  \  "  '  <space>  <tab>  <newline>

Quoting can be done in 3 ways

• Escape character \
• Single-Quotes '
• Double-Quotes "

Escape character - backslash \

Can be either a line break or an escape character

Single Quote '

Preserves the meaning of all characters until the next ' is encountered. A single quote cannot occur within single quotes

valgrind alias

alias minival='valgrind --show-leak-kinds=all --leak-check=full --suppressions=vg_rlsuppressions.supp'