MangiShell

Usage

1. make
2. ./a.out

Assumptions

• Path sizes are at max 1024 character
• Max character limit of a executable is 256 characters
• History file should not be deleted during execution of the shell, it leads to a segmentation fault and it's not my fault.
• In the implementation of jobs , there can be at most 1022 background processes.

Features

; separated commands

• You can run more than 1 shell command in a single line by separating them with a ;

ls

• Displays the contents of a directory if specified, else displays contents of current directory.
• Add -l to display the details of each file.
• Add -a to display the hidden contents.
• The directories and flags can be mentioned in any order after ls

cd

• change the current working directory to the relative or the absolute path passed as argument.
• supports paths of the form ~/ , ./ , ../
• ~ to go back to the shell executable directory, this acts as the home directory of the shell.
• .. to go to the previous directory. If you go behind the home directory of shell, the absolute path is printed in the prompt instead.
• - will change your directory to the previous directory you were in.
• no arguments passed change the directory to home directory.

pwd

• To see the present working directory pwd.

pinfo

• Displays the process information.
  • Process ID
  • Process Status
  • Virtual memory
  • executable path.
• If the PID is not mentioned it will show the information about the shell process.
• If PID does not exist, then error is thrown.

Discover

• discover Prints all the contents of a directory in a recursive manner. If no path is specified, then the command runs on current directory.
• The paths are printed in alphabetical order, and in a breadth-first search manner.
• Flag -f may be used to list only all the file paths.
• Flag -d may be used to list only all the directory paths.

History

• Displays the last 10 used commands with most recent ones appearing at the bottom of the list.
• Stores upto 20 history commands.
• Implemented using a hidden file named .history.txt

File redirection

• < is used for input redirection. cat < input.txt File contents of input are redirected to stdin and cat is executed.
• > is used for output redirection. ls > output.txt the output of ls is redirected to output file. This is also called the truncate mode, since it overwrites the file output.txt if it exists.
• >> is used for output redirection in append mode. It appends the data to the file it is redirected into.
• Both input and output redirection can be combined together in a single command.

Piping

• | Can be used to redirect one commands output to another file. For instance, ls | wc Will redirect the output of ls to wc.
• More than 2 commands can be chained together for piping.
• Input Output redirection using >,< and >> can also be done in piping

Jobs

• Jobs are processes spawned by the shell, jobs will list the background processes spawned by the shell along with their status and the pid in the order in which they were spawned.
• jobs -r will list all the running processes.
• jobs -s will list all the stopped processes.
• signal job_number signal_number Will send the signal to the given job.
• exit Will exit out of the shell.

Signal handling

• Ctrl+Z will kill send the current foreground process to the background and will stop the process.
• Ctrl+C will interrupt the currently running foreground process, if no foreground process is present, it will do nothing.
• Ctrl+D Will Exit out of the shell.

fg/bg

• fg can be used to bring a background process to the foreground process. The shell will only continue to execute after the process has terminated.
• bg can be used to make a stopped background process run again.