RUNNING THE SHELL

run make to generate the executable

run ./shell to run the shell

run quit to exit the shell

FEATURES

Foreground processes

• The shell waits for the current process to execute

Background processes

• Use '&' at the end of any command to invoke a background process
• The process will then run in the background and when exited, a message will be displayed

ls command

• ls takes arguments as flags (as -) and directories (as )
• It lists the files of the directory mentioned. If no directory is mentioned, it lists the files in the current directory
• ls - lists in alphabetical order
• ls -l - long list
• ls -a - display hidden files
• ls -al/-la/-a -l/-l -a - long list including hidden files

cd command

• cd <absolute path> - goes to absolute path
• cd - goes to ~/
• cd ~/<pathname> - goes to ~/
• cd .. - goes to previous directory
• cd . - stays in the same directory

echo command

• echo - prints empty line
• echo text - prints text
• echo "text" / echo 'text' - prints text

pwd command

• pwd - prints absolute path of current directory

pinfo command

• pinfo - prints process info of the shell
• pinfo <pid> - prints process info of given pid

Input/Output redirection

• Ouput of one command can be redirected to a file
• Similarly input can be taken from another file

Redirection using Pipes

• One or more commands can be piped
• Pipes and i/o redirection can be done together

Environment variables

• The shell inherits environment variables from the parent
• setenv var value - used to create environment variable var
• unsetenv var - destroy the variable var

jobs command

• jobs - prints a list of all background processes

kjob command

• kjob <jobnumber> <signal> - takes the job id of a running job and sends a signal value to that process

fg command

• fg <jobnumber> - brings a running or a stopped background job with given job number to foreground

bg command

• bg <jobnumber> - changes a stopped background job to a running background job

overkill command

• overkill - kills all background process at once

quit command

• quit - exit the shell. The shell exits only when quit is typed

Signals

• CTRL+C - sends a SIGINT signal to the foreground jobs of the shell and not the shell itself and neither to the background processes of the shell
• CTRL+Z - sends a SIGTTIN and SIGTSTP signal to the foreground process and makes the process a background process

ADITIONAL FEATURES

reminder

• type remindme <no of seconds> "task" to set a reminder

clock

• type clock -t <interval time> -n <duration> to display the date and time after specified interval and for the specified duration
• made using hardware clock "/sys/class/rtc/rtc0"