nanafox / simple_shell

This is a minimal version of the original 'sh' shell (Bourne Shell)

MSH (Minimal Shell)

MSH is a minimalistic shell implementation that provides a basic command-line interface with enhanced features. This README outlines the various functionalities supported by MSH.

Table of Contents

• MSH (Minimal Shell)
  • Table of Contents
    • Change Directory (cd)
    • Alias and Unalias
      • Usage:
    • Logical Operators (&& and ||)
      • Example:
    • System Commands
      • Example:
    • Exit Command
      • Example:
    • Setenv and Unsetenv
      • Example:
    • File as Input
      • Example:
    • Comments
      • Example:
    • Variable Expansion
      • Example:
    • Command Separator (;)
      • Example:
    • Custom Env
      • Example:
    • PATH
    • Commands with and without Arguments
      • Examples:
  • Releases
  • Download and Usage
  • Author

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Change Directory (cd)

The cd command is built into MSH, allowing users to change the current working directory. Simply enter cd [directory] to navigate to the specified directory. If [directory] is omitted, the current user's $HOME directory is used. This cd also handles the - argument that's passed to the cd command. For example, when the command is cd -, the shell changes directory to the value of $OLDPWD, which is the last directory the user visited before their current working directory.

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Alias and Unalias

MSH supports aliasing commands for convenience using the alias command and removing aliases with unalias. This enables users to create shorthand notations for commonly used commands.

Usage:

alias cls='clear'
alias md=mkdir

# Improved usage
alias ls="ls --color=auto" ping="ping -c 5"
alias memchk='valgrind --leak-check=full --show-leak-kinds=all --track-origins=yes -s'
alias flush_dns_cache=""
alias lsfwrules='sudo iptables -nv --line-numbers -L '
.
.
.
alias flush_dns_cache='resolvectl flush-caches'
alias l1="ls -1"
alias grep='grep --color=auto'

unalias cls # remove the 'cls' alias

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Logical Operators (&& and ||)

Logical operators && (AND) and || (OR) are supported in MSH. They enable users to execute commands conditionally based on the success or failure of previous commands.

Example:

command1 && command2
command1 || command3

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System Commands

MSH allows the execution of system commands. Enter any system command directly in the shell prompt to run it.

Example:

ls -a
cat /etc/passwd
mkdir src

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Exit Command

The exit command, built into MSH, is used to exit the shell gracefully. It takes positive exit codes

Example:

exit
exit 1 # exit with status code 1

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Setenv and Unsetenv

The setenv and unsetenv commands are utilized to set and unset environment variables, respectively. This feature enhances the customization of the shell environment.

Example:

setenv MY_VARIABLE my_value
unsetenv MY_VARIABLE

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File as Input

MSH can take input from a file, allowing users to execute a series of commands from a script.

Example:

msh script.txt

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Comments

Comments can be added to MSH using the # symbol, allowing users to annotate their commands without affecting execution.

Example:

# This is a comment
echo "Hello, MSH!"

ls # this will list the contents in the current working directory

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Variable Expansion

MSH supports variable expansion, including $$ (current process ID) and $? (exit status of the last executed command).

Example:

echo "Process ID: $$"
command
echo "Exit Status: $?"

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Command Separator (;)

The semicolon (;) acts as a command separator in MSH, allowing users to execute multiple commands on a single line.

Example:

command1 ; command2

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Custom Env

Custom command env is available to display the current environment variables.

Example:

env

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PATH

MSH uses the PATH environment variable to locate executable files. Ensure the desired directories are included in the PATH for seamless command execution.

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Commands with and without Arguments

MSH supports commands with and without arguments, providing flexibility in command execution.

Examples:

ls
ls -l

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Releases

• Latest Release
• All Releases

Download and Usage

To download the latest release of MSH, click here.

For information on how to install and execute, please visit the wiki

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Author

Maxwell Nana Forson

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