COMP 3000 Lab 3 2011 - Revision history

Saran: /* Part A */

2011-10-31T01:05:16Z

Part A

← Older revision		Revision as of 01:05, 31 October 2011
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	<li> renice </li>		<li> renice </li>
	<li> run-program-reverse.c </li>		<li> run-program-reverse.c </li>
	<li> sanitize-env.c </li>		<li> sanitize-env.c. Run it with /usr/bin/env </li>
	</ol>		</ol>

Saran: /* Part A */

2011-10-27T20:27:58Z

Part A

← Older revision		Revision as of 20:27, 27 October 2011
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	<li> <ol style="list-style-type: lower-alpha;">		<li> <ol style="list-style-type: lower-alpha;">
	<li>SIGSEGV or SIGBUS is raised for invalid memory references. SIGBUS is low level device specific signal. The following program generates a SIGSEGV in my computer : int a; a = 10; </li>		<li>SIGSEGV or SIGBUS is raised for invalid memory references. SIGBUS is low level device specific signal. The following program generates a SIGSEGV in my computer : int a; a = 10; </li>
	<li> SIGSTOP for pausing, and SIGCONT for continuing.		<li> SIGSTOP (which cannot be caught) or SIGTSTP (can be caught) for pausing, and SIGCONT for continuing.
	You can use "kill -SIGWHATEVER pid" from the terminal, or from code. For ex :		You can use "kill -SIGWHATEVER pid" from the terminal, or from code. For ex :
	pause-and-cont.c </li>		pause-and-cont.c </li>

Saran: /* Answers */

2011-10-27T20:18:04Z

Answers

← Older revision		Revision as of 20:18, 27 October 2011
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	=Answers=		=Answers=
	~~Both Parts Graded~~ by Saran. Email him for any queries.		All questions graded by Saran. Email him for any queries.
	==Part A==		==Part A==

Saran: /* Answers */

2011-10-27T20:17:49Z

Answers

← Older revision		Revision as of 20:17, 27 October 2011
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	=Answers=		=Answers=
			Both Parts Graded by Saran. Email him for any queries.
	==Part A==		==Part A==

Saran: /* Part A */

2011-10-27T20:08:45Z

Part A

← Older revision		Revision as of 20:08, 27 October 2011
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	</ol>		</ol>
	<li>What command can lower the priority of an already running process? (1 mark)		<li>What command can lower the priority of an already running process? (1 mark)
	<li>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''.(2 marks) </li>		<li>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''. (2 marks) </li>
	<li>Create ''sanitize-env.c'' that does the same as run-program.c except it exec's the program with all environment variables stripped except the PATH and TERM variables (assuming they are defined). Be sure to document how you tested your program. (2 marks)		<li>Create ''sanitize-env.c'' that does the same as run-program.c except it exec's the program with all environment variables stripped except the PATH and TERM variables (assuming they are defined). Be sure to document how you tested your program. (2 marks)
	</ol>		</ol>

Saran: /* Part A */

2011-10-27T20:08:37Z

Part A

← Older revision		Revision as of 20:08, 27 October 2011
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	</ol>		</ol>
	<li>What command can lower the priority of an already running process? (1 mark)		<li>What command can lower the priority of an already running process? (1 mark)
	<li>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''.(2 ~~mark~~) </li>		<li>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''.(2 marks) </li>
	<li>Create ''sanitize-env.c'' that does the same as run-program.c except it exec's the program with all environment variables stripped except the PATH and TERM variables (assuming they are defined). Be sure to document how you tested your program. (2 ~~mark~~)		<li>Create ''sanitize-env.c'' that does the same as run-program.c except it exec's the program with all environment variables stripped except the PATH and TERM variables (assuming they are defined). Be sure to document how you tested your program. (2 marks)
	</ol>		</ol>

Saran: /* Part B */

2011-10-27T20:08:03Z

Part B

← Older revision		Revision as of 20:08, 27 October 2011
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	<ol>		<ol>
	<li value=6> Create a simple program ''receive-usr1.c'' that uses sigaction in order to print "Ouch!" when you send the program the USR1 signal. Note that your program should not consume much CPU time while waiting (i.e., do not poll for the signal).</li>		<li value=6> Create a simple program ''receive-usr1.c'' that uses sigaction in order to print "Ouch!" when you send the program the USR1 signal. Note that your program should not consume much CPU time while waiting (i.e., do not poll for the signal).(2 marks)</li>
	<li> Create a simple program ''nocrash.c'' that accesses an invalid pointer but then prints "Oops, my mistake" rather than crash.</li>		<li> Create a simple program ''nocrash.c'' that accesses an invalid pointer but then prints "Oops, my mistake" rather than crash.(2 marks) </li>
	<li> Create a program ''run-program-dots.c'' that works the same as run-program.c, except that it prints one dot every second while a given program runs. Note that it should stop printing dots once the exec'd program terminates. Your solution should use the fork(), sleep(), execve(), and sigaction() calls.</li>		<li> Create a program ''run-program-dots.c'' that works the same as run-program.c, except that it prints one dot every second while a given program runs. Note that it should stop printing dots once the exec'd program terminates. Your solution should use the fork(), sleep(), execve(), and sigaction() calls.(2 marks)</li>
	<li> What is the difference between the PR and NI columns in the top command? Explain in the context of running a CPU-intensive program. (Hint: you should try running a CPU intensive program or two and observe these columns...)</li>		<li> What is the difference between the PR and NI columns in the top command? Explain in the context of running a CPU-intensive program. (Hint: you should try running a CPU intensive program or two and observe these columns...) (1 mark)</li>
	</ol>		</ol>

Saran: /* Part A */

2011-10-27T20:07:40Z

Part A

Saran: /* Part A */

2011-10-27T18:52:28Z

Part A

← Older revision		Revision as of 18:52, 27 October 2011
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	<ol>		<ol>
	<li value=6> Compile and run receive-usr1.c and issue "kill -SIGUSR1 pid" </li>		<li value=6> Compile and run receive-usr1.c and issue "kill -SIGUSR1 pid" </li>
	<li> Use gdb to figure out what signal is thrown for invalid pointer accesses, then catch that. </li>		<li> Use gdb to figure out what signal is thrown for invalid pointer accesses, then catch that. nocrash.c </li>
	<li> run-program-dots.c </li>		<li> run-program-dots.c </li>
	<li>NI is the nice value of a process, which can be changed by the user. It ranges from -20 to 19 and is used as an input to the scheduler. Depending on all other processes and available resources, the scheduler decides the priority of a process and displays its calculated value in the PR column.		<li>NI is the nice value of a process, which can be changed by the user. It ranges from -20 to 19 and is used as an input to the scheduler. Depending on all other processes and available resources, the scheduler decides the priority of a process and displays its calculated value in the PR column.

Saran at 18:51, 27 October 2011

2011-10-27T18:51:41Z

Show changes

← Older revision		Revision as of 20:07, 27 October 2011
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	<li>Compile run-program.c with the command ''gcc -g run-program.c -o run-program'' and use it to answer the following questions.</li>		<li>Compile run-program.c with the command ''gcc -g run-program.c -o run-program'' and use it to answer the following questions.</li>
	<ol style="list-style-type: lower-alpha;">		<ol style="list-style-type: lower-alpha;">
	<li> Is the line "Is this line printed?" printed when you execute '''./run-program /bin/ls -a /tmp'''? Why?		<li> Is the line "Is this line printed?" printed when you execute '''./run-program /bin/ls -a /tmp'''? Why? (1 mark) </li>
	<li> Change the program to use execve instead of execvp. What is the difference between the two system calls? </li>		<li> Change the program to use execve instead of execvp. What is the difference between the two system calls? (1 mark) </li>
	</ol>		</ol>
	<li> Linux signals is a simple form of IPC that is used for a variety of purposes.</li>		<li> Linux signals is a simple form of IPC that is used for a variety of purposes.</li>
	<ol style="list-style-type: lower-alpha;">		<ol style="list-style-type: lower-alpha;">
	<li> What signal is generated when a program attempts to dereference an invalid pointer? Give a simple program that generates such a signal.</li>		<li> What signal is generated when a program attempts to dereference an invalid pointer? Give a simple program that generates such a signal.(1 mark) </li>
	<li> How would you send a signal to a process to have it pause execution? Resume?</li>		<li> How would you send a signal to a process to have it pause execution? Resume? (1 mark) </li>
	</ol>		</ol>
	<li>What command can lower the priority of an already running process?		<li>What command can lower the priority of an already running process? (1 mark)
	<li>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''.</li>		<li>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''.(2 mark) </li>
	<li>Create ''sanitize-env.c'' that does the same as run-program.c except it exec's the program with all environment variables stripped except the PATH and TERM variables (assuming they are defined). Be sure to document how you tested your program.		<li>Create ''sanitize-env.c'' that does the same as run-program.c except it exec's the program with all environment variables stripped except the PATH and TERM variables (assuming they are defined). Be sure to document how you tested your program. (2 mark)
	</ol>		</ol>