COMP 3000 Lab 3 2011

Please answer using text files. Do not use doc, docx, pdf etc. Submit your solutions via WebCT by October 21st at 8 PM.

Part A (in Tutorial)

Notes:

• execve example
• fork, execve example
• generate, receive user signal
• change scheduling priorities program

1. Compile run-program.c with the command gcc -g run-program.c -o run-program and use it to answer the following questions.
   1. Is the line "Is this line printed?" when you execute ./run-program /bin/ls -a /tmp? Why?
   2. Change the program to use execve instead of execvp . What is the new line?
2. Linux signals is a simple form of IPC that is used for a variety of purposes.
   1. What signal is generated when a program attempts to dereference an illegal pointer? Give a simple program that generates such a signal.
   2. How would you send a signal to a process to have it pause execution? Resume?

Part B (on your own)

• catch segfault signal, sigchild?
• make very simple shell based on skeleton?
• run fork bomb, play with priorities to reduce impact, set quota

1. Create run-program-reverse.c that is the same as run-program.c except that it interprets its arguments in reverse order. Hence, ./run-program-reverse /tmp -a /bin/ls will do the same as ./run-program /bin/ls -a /tmp.

Program Listings

/* run-program.c */

#include <unistd.h>
#include <stdio.h>

int main( int argc, char *argv[], char *envp[] ) {

   if( argc < 2 ) {
       printf( "Insufficient arguments.\n" );
       return -1;
   }
   execvp( argv[1], argv + 1 );
   printf( "Is this line printed?\n" );
   return 0;
}