Operating System and Networks Assignment 3 Extending Cshell

---

Project Structure:

2021121005_Assignment3
├─ a.out
├─ bg.c
├─ cd.c
├─ delete_comm.c
├─ duplicate.c
├─ echo.c
├─ fg.c
├─ headers.h
├─ history.c
├─ jobs.c
├─ ls.c
├─ main.c
├─ makefile
├─ pinfo.c
├─ pipecom.c
├─ prompt.c
├─ prompt.h
├─ pwd.c
├─ repeat.c
├─ replay.c
├─ signals.c
├─ split.c
└─ syscom.c

How to run ?: compile the make file in the dircetory which compiles all the files required for the project and then execute ./a.out(in linux).

Commands implemented:

• cd: Changes the current directory (implmented with special flags like ~,-).Implemented in cd.c

• echo: Outputs/prints the given arguments to the terminal.Implemented in echo.c

• pwd: Outputs/prints the current working directory to the terminal.Implemented in pwd.c

• ls: Lists the contents of the directory (implemented with various flags like

  • -l :long contents which displays variety of details regarding the files
  • -a :displays even hidden files
  • -la: long and hidden files
  • -l {dir} -a {dir} ,etc:

  Implemented in ls.c

• System commands: Systems commands can be executed within background or foreground using & flag. Eg:

  • gedit & runs in background
  • gedit runs in foreground Implemented in syscom.c

• pinfo: pinfo command is used for displaying process information .displays the info of calling process by default and displays the info of the pid when argument pid is passed.Implemented in pinfo.c

• repeat: Repeats a command for n number of times .Implemented in repeat.c

• history: Outputs the history of commands typed in(default no of commands outputed =20).Implemented in history.txt

• Note: the history command leads t0 create a directory in the home directory with file name as 2021121005history.txt.

• Input/output redirection: The shell can handle both input and output redirection individually and simultaneously as well. Implemented in main.c

  • "<" for Inpur redirection
  • ">" for out put redirection(writes the file given in argument) .
  • ">>" for output redirection appends to the file given in argument.

• piping: The shell can handle pipe commands (i.e, output of one pipe is sent as input to anothe pipe) seperated by "|" . The program can even handle the cases where input and output redirection commands are given in pipe commands .Implemented in pipecom.c

• jobs: prints the current jobs in the background with theire status and pid and job number.Implemented in jobs.c(implemented with flags -r, -s).

• bg Brings a stopped background process to running status.Implemented in bg.c

• fg Brings a running/stopped background process to foreground.implemented in fg.c.

• sig Passes a specified signal to the specified job number. Implemented in signals.c

• signal handling:

  • ctrl-z: stops the current executing foreground process without stopping the parent shell process.

  • ctrl-c: Interrupts the current executing foreground process without interrupting the parent shell process.

  • ctrl-d: Terminated the shell without causing distubance to the original terminal.

• replay (Bonus): replay a command for every given amount of seconds and till upto a finite number of given seconds.Implemented in replay.c

---

P Shiridi Kumar : 2021121005