Scribd
Upload
22 views1 page

Assign 4 S 24

The assignment requires the implementation of a simple shell program named 'uish' for the University of Idaho. It must execute Unix/Linux commands, support shell variables including PATH, and handle background execution with the '&' symbol. The shell should use the fork/exec mechanism and wait for command completion before prompting for the next command, except for background tasks.

Uploaded by

pratik.rauniyar
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
22 views1 page

Assign 4 S 24

The assignment requires the implementation of a simple shell program named 'uish' for the University of Idaho. It must execute Unix/Linux commands, support shell variables including PATH, and handle background execution with the '&' symbol. The shell should use the fork/exec mechanism and wait for command completion before prompting for the next command, except for background tasks.

Uploaded by

pratik.rauniyar
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
You are on page 1/ 1

#4

CS240 - Operating Systems


Assignment #4
Spring 2024

For this exercise, you are to implement a simple “shell” program, similar to a simple bash
shell. Call your shell uish (for “University of Idaho shell”).

• When invoked it should produce a prompt: $

• You should be able to enter any Unix/Linux command name, including options, and the
program should execute properly. Your shell should parse the input, then execute the
command using the fork/exec mechanism.

• Your shell should support shell variables. You should be able to define variables and use

ign
them in shell commands:

ABC=xyz
echo $ABC

• One shell variable that should be used is PATH. This should work just like the “real” shell.
That is, once defined, it should prepend each file prefix in the PATH variable until either
it finds an executable, or it goes through the full list and doesn’t find a match, in which
case your shell should print an error message, similar to the real shell. NOTE that your
shell should use execv() (rather than execp() or execvp()), since your program should
do the PATH processing.

• Your shell should wait until the command completes, then it should issue another prompt
and be able to accept another command. EXCEPT:
Ass
• Your shell should support “background” execution. That is, if the command contains
the ’&’ (ampersand) at the end, your shell should launch the command, but return im-
mediately, displaying the prompt and be ready to accept another command.

As before, your program should not use the real shell for any processing, other than to start
your program.

You might also like