alexwilso / smallsh Goto Github PK

Author: Alex Wilson

Date: October 27 2021

Description: The following program is a shell created using C. The shell has the following fearures...

    1. Provide a prompt for running commands
    2. Handle blank lines and comments, which are lines beginning with the # character
    3. Provide expansion for the variable $$
    4. Execute 3 commands exit, cd, and status via code built into the shell
    5. Execute other commands by creating new processes using a function from the exec family of functions
    6. Support input and output redirection
    7. Support running commands in foreground and background processes
    8. Implement custom handlers for 2 signals, SIGINT and SIGTSTP


Compile the program as follows:
    Launch terminal
    cd into directory containing main.c file.
    Run command in terminal: gcc --std=gnu99 -o smallsh main.c
    Run command in terminal: ./smallsh

Example.

$ smallsh
: ls
junk   smallsh    smallsh.c
: ls > junk
: status
exit value 0
: cat junk
junk
smallsh
smallsh.c
: wc < junk > junk2
: wc < junk
       3       3      23
: test -f badfile
: status
exit value 1
: wc < badfile
cannot open badfile for input
: status
exit value 1
: badfile
badfile: no such file or directory
: sleep 5
^Cterminated by signal 2
: status &
terminated by signal 2
: sleep 15 &
background pid is 4923
: ps
  PID TTY          TIME CMD
 4923 pts/0    00:00:00 sleep
 4564 pts/0    00:00:03 bash
 4867 pts/0    00:01:32 smallsh
 4927 pts/0    00:00:00 ps
:
: # that was a blank command line, this is a comment line
:
background pid 4923 is done: exit value 0
: # the background sleep finally finished
: sleep 30 &
background pid is 4941
: kill -15 4941
background pid 4941 is done: terminated by signal 15
: pwd
/nfs/stak/users/chaudhrn/CS344/prog3
: cd
: pwd
/nfs/stak/users/chaudhrn
: cd CS344
: pwd
/nfs/stak/users/chaudhrn/CS344
: echo 4867
4867
: echo $$
4867
: ^C^Z
Entering foreground-only mode (& is now ignored)
: date
 Mon Jan  2 11:24:33 PST 2017
: sleep 5 &
: date
 Mon Jan  2 11:24:38 PST 2017
: ^Z
Exiting foreground-only mode
: date
 Mon Jan  2 11:24:39 PST 2017
: sleep 5 &
background pid is 4963
: date
 Mon Jan 2 11:24:39 PST 2017
: exit
$