Zeesh - Shell in C

Introduction

Shell with some basic functionalities written in C with the help of system header files.

How to use

• Clone the directory
• run make inside the directory.
• ./z to run the shell.
• exit to exit out of the shell.

Features

Built-in features

Indentation insensitive

Regardless of where you write the command by adding spaces or tabs, it will behave in the same way.

; separated commands

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

ls

• Lists the contents of the given 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.
• ~ to go back to the shell executable directory.
• .. to go to the previous directory.
• - will change your directory to the previous directory you were in.

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.

History

• Displays the last used commands with most recent ones appearing at the bottom of the list.
• stores uptill 20 history commands.

Nightswatch [incomplete]

• gives the output of 2 particular commands continuously till interrupted.
• nightswatch -n [time] {interrupt/newborn}
• interrupt:
  • Shows the number of keyboard interrupts handled by each CPU
• newborn:
  • Shows the last run process on the system.

File redirection

• < is used for input redirection. cat < input File contents of input are redirected to stdin and cat is executed.
• > is used for output redirection. ls > output the output of ls is redirected to output file.
• Both of them can be combined together in a single command.

Piping

• | Can be used to redirect one commands output to another file. ls | wc Will redirect the output of ls to wc.
• More than 2 commands can be chained together for piping.

Environment variables

• setenv can be used to overwrite the value of a environment variable to the given value.
• unsetenv can be used to remove the variable from the environment.
• getenv can be used to print the value of the given environment variable.

Jobs

• Jobs are processes spawned by the shell, jobs will list the processes spawned by the shell along with their status and the pid.
• kjob job_number signal_number Will send the signal to the given job.
• overkill Will kill all background processes at once.
• 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.

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.