mini-unix-shell

Implementation of a Unix-like shell with job control in C.

Running

To run the code, do:

make
./crash

It runs external programs with fork/execvp, background jobs with &, and has built-in support for jobs, fg, bg, nuke and quit, along with signal handling.

Shell Scripts

This repo also contains simple shell scripts that test and demonstrate the job control features.

Both scripts build crash and run a scripted session against it, printing out a small PASS/FAIL summary based on the expected output.

test_crash.sh starts two background sleep jobs, runs nuke %1 and checks that both jobs reached the running sleep state and that at least one killed sleep appeared in the output.

test_crash_fg_bg.sh tests the suspend and resume behavior for foreground and background jobs. It suspends a foreground sleep with SIGTSTP (equivalent to pressing Ctrl+Z when we're using crash), suspends a background sleep and resumes it with bg <PID>, and checks for the suspended, continued and killed messages for each PID.

To run them:

chmod +x test_crash.sh test_crash_fg_bg.sh

./test_crash.sh
./test_crash_fg_bg.sh

More thorough testing can (and should when making changes) be done by actually putting the inputs in directly as shown below.

Example Inputs

Once you get crash running (see above), here are some simple tests you can do to verify the appropriate output. Your order of interruption (i.e. when you get the finished sleep message) may vary depending on your typing speed, but other than that putting the instructions in in the same order should yield the same results.

General Usage

crash> sleep 30 &
[1] (19887)  running  sleep
crash> jobs 
[1] (19887)  running  sleep
crash> sleep 20 &
[2] (20002)  running  sleep
crash> jobs
[1] (19887)  running  sleep
[2] (20002)  running  sleep
crash> sleep 30
^Z[3] (20055)  suspended  sleep
crash> jobs
[1] (19887)  running  sleep
[2] (20002)  running  sleep
[3] (20055)  suspended  sleep
crash> bg %3
crash> [3] (20055)  continued  sleep
jobs
[1] (19887)  running  sleep
[2] (20002)  running  sleep
[3] (20055)  running  sleep
crash> fg %1
^C[1] (19887)  killed  sleep
crash> jobs
[2] (20002)  running  sleep
[3] (20055)  running  sleep
crash> [2] (20002)  finished  sleep
nuke %3
[3] (20055)  killed  sleep
crash> jobs
crash> quit

Bad Inputs

crash> fg
ERROR: fg needs exactly one argument
crash> fg %99
ERROR: no job 99
crash> nuke 12x
ERROR: bad argument for nuke: 12x