tushar994 / linux-shell-in-c

tushell

what is this?

This is a linux shell implemented in c

Functionality

supports ';', piping and redirection (<, > , >>).

signals CTRL+Z and CTRL+C are handled.

The built in commands are :-- ls (-al), echo, pwd, cd, pinfo, history, nightswatch(both interrupt and newborn), setenv var [value], unsetenv var, jobs kjob <job number> <signal number> , fg <job number>, bg <job number>, overkill, quit.

it prints out a prompt in the form of <username@system_name:curr_dir>

it prints :') before the prompt if the previous command executed normally, otherwise prints :'(

can create background process using an & at the end of the command

displays <command name> with pid <pid> exited with code <exit code> when a background process ends

RUNNING

to run

$ make
$ ./tushell

how to exit

to exit

$ quit

or

$ ^D

inside the program. This kills all bbackground processes created by the program and then terminates. ^C might not do the same and can sometimes give errors

Files Wise code breakdown

• shell.c : this is where the shell runs from.
• bg.c : where background processes are created, and where jobs, kjob, fg, bg are implemented.
• fg.c : where the foreground process runs from
• change_dir.c : where cd is implemented
• echo.c : where echo is implemented.
• exit.c : where the quit and overkill is implemented
• get_prompt.c : where pwd and printing the prompt is implemented
• history.c : this creates a file called history_tush.txt WHEREVER THE TERMINAL IS RUN FROM. So if you run it from two different locations, it gives different histories for them.
• ls.c : where ls is outputted from. flags -l,-a,-la,-al are implemented. It outputs everything in a column (even if -l is not specified).
• nightswatch.c : where nightswatch is implemented. it exits the loop with "q\n". by default it executes every 5 seconds.
• pinfo.c : this is where pinfo is implemented

in-build commands

-pwd, cd, echo are in-built. teh command cd - is valid and goes to the previous working directory.

• ls [-la] is in-built. Even if [-l] is not specified, it outputs the file names in a column.
• pinfo [pid(optional)] is in-built.
• history [number (optional)] is in-built. by default it gives the last 10. if it has to give n previous commands, but it has stored less commands, then it outputs all the commands it can output. Number has to be a two-digit (or one-digit) number.