Operating Systems 2022F: Assignment 2 - Revision history

Soma at 15:30, 11 October 2022

2022-10-11T15:30:51Z

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	}		}
	</syntaxhighlight>		</syntaxhighlight>

			==Solutions==

			[https://homeostasis.scs.carleton.ca/~soma/os-2022f/solutions/a2-sol.txt Assignment 2 solutions]

Soma at 02:50, 2 October 2022

2022-10-02T02:50:11Z

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	~~'''This assignment is not yet finalized.'''~~

	Please submit the answers to the following questions via Brightspace by October 11, 2022 by 11:30 AM. There are 20 points in 10 questions.		Please submit the answers to the following questions via Brightspace by October 11, 2022 by 11:30 AM. There are 20 points in 10 questions.

Soma: /* Questions */

2022-10-02T02:43:13Z

Questions

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	<ul>		<ul>
	<li>a file to be opened for standard input,</li>		<li>a file to be opened for standard input,</li>
	<li>a file to be opened for standard output (and ~~created~~ if necessary),</li>		<li>a file to be opened for standard output (erasing any existing file and creating it if necessary),</li>
	<li>a file to be opened for standard error (and created if necessary), and</li>		<li>a file to be opened for standard error (erasing any existing file and created it if necessary), and</li>
	<li>a program to run (either an absolute path or a program in the current PATH) with zero or more arguments.</li>		<li>a program to run (either an absolute path or a program in the current PATH) with zero or more arguments.</li>
	</ul>		</ul>

Soma: /* Questions */

2022-10-01T21:13:47Z

Questions

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	==Questions==		==Questions==

	# [2] What internal commands does 3000shell2.c support? Are these the same as those supported by 3000shell.c? Explain briefly.		<ol>
	# [2] If you build 3000shell2.c the same as you did 3000shell.c (from Tutorial 3, the given gcc command), what does the command "pinfo" report? What about if you build it as you did 3000userlogin.c (from Tutorial 4, the Makefile)? Explain any differences you see.		<li>[2] What internal commands does 3000shell2.c support? Are these the same as those supported by 3000shell.c? Explain briefly.</li>
	# [2] What is the purpose of lines 188 and 189 (the calls to seteuid() and setegid())? Do they always do something useful?		<li>[2] If you build 3000shell2.c the same as you did 3000shell.c (from Tutorial 3, the given gcc command), what does the command "pinfo" report? What about if you build it as you did 3000userlogin.c (from Tutorial 4, the Makefile)? Explain any differences you see.</li>
	# [1] What is the syntax of the "become" command?		<li>[2] What is the purpose of lines 188 and 189 (the calls to seteuid() and setegid())? Do they always do something useful?</li>
	# [1] What must be true for the "become" command to work?		<li>[1] What is the syntax of the "become" command?</li>
	# [2] Modify the "become" command so it takes a uid, not just a username.		<li>[1] What must be true for the "become" command to work?</li>
	# [2] How does the behavior of 3000shell2 change when it is run setuid root versus running as root? Why?		<li>[2] Modify the "become" command so it takes a uid, not just a username.</li>
	# [2] Does output redirection work for any of the internal commands? Explain briefly.		<li>[2] How does the behavior of 3000shell2 change when it is run setuid root versus running as root? Why?</li>
	# [4] Create a command "background" that runs a program in the background, redirecting standard in, out, and error. background takes at least four arguments:		<li>[2] Does output redirection work for any of the internal commands? Explain briefly.</li>
	#* a file to be opened for standard input,		<li>[4] Create a command "background" that runs a program in the background, redirecting standard in, out, and error. background takes at least four arguments:
	#* a file to be opened for standard output (and created if necessary),		<ul>
	#* a file to be opened for standard error (and created if necessary), and		<li>a file to be opened for standard input,</li>
	#* a program to run (either an absolute path or a program in the current PATH) with zero or more arguments.		<li>a file to be opened for standard output (and created if necessary),</li>
	# [2] How can you ensure that the new "background" can be combined with the "become" command? Why does this work?		<li>a file to be opened for standard error (and created if necessary), and</li>
			<li>a program to run (either an absolute path or a program in the current PATH) with zero or more arguments.</li>
			</ul>
			Note that background should ignore any > or & characters included.
			</li>
			<li>[2] How can you ensure that the new "background" can be combined with the "become" command? Why does this work?</li>
			</ol>

	==Code==		==Code==

Soma: /* Questions */

2022-10-01T03:22:58Z

Questions

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	# [2] What internal commands does 3000shell2.c support? Are these the same as those supported by 3000shell.c? Explain briefly.		# [2] What internal commands does 3000shell2.c support? Are these the same as those supported by 3000shell.c? Explain briefly.
	# [2] If you build 3000shell2.c the same as you did 3000shell.c (from Tutorial 3, the given gcc command), what does the command "pinfo" report? What about if you build it as you did 3000userlogin.c (from Tutorial 4, the Makefile)? Explain any differences you see.		# [2] If you build 3000shell2.c the same as you did 3000shell.c (from Tutorial 3, the given gcc command), what does the command "pinfo" report? What about if you build it as you did 3000userlogin.c (from Tutorial 4, the Makefile)? Explain any differences you see.
	# [2] What is the purpose of lines ~~190~~ and ~~191~~ (the calls to seteuid() and setegid())? Do they always do something useful?		# [2] What is the purpose of lines 188 and 189 (the calls to seteuid() and setegid())? Do they always do something useful?
	# [1] What is the syntax of the "become" command?		# [1] What is the syntax of the "become" command?
	# [1] What must be true for the "become" command to work?		# [1] What must be true for the "become" command to work?

Soma: /* Questions */

2022-10-01T03:18:12Z

Questions

← Older revision		Revision as of 03:18, 1 October 2022
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	# [2] What internal commands does 3000shell2.c support? Are these the same as those supported by 3000shell.c? Explain briefly.		# [2] What internal commands does 3000shell2.c support? Are these the same as those supported by 3000shell.c? Explain briefly.
	# [2] If you ~~compile~~ 3000shell2.c the same as you did 3000shell.c (from Tutorial 3), what does the command "pinfo" report? What about if you ~~compile~~ it as you did 3000userlogin.c (from Tutorial 4)? Explain any differences you see.		# [2] If you build 3000shell2.c the same as you did 3000shell.c (from Tutorial 3, the given gcc command), what does the command "pinfo" report? What about if you build it as you did 3000userlogin.c (from Tutorial 4, the Makefile)? Explain any differences you see.
	# [2] What is the purpose of lines 190 and 191 (the calls to seteuid() and setegid())? Do they always do something useful?		# [2] What is the purpose of lines 190 and 191 (the calls to seteuid() and setegid())? Do they always do something useful?
	# [1] What is the syntax of the "become" command?		# [1] What is the syntax of the "become" command?

Soma: /* Code */

2022-10-01T03:17:25Z

Code

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	{		{
	int result;		int result;
	~~char *shell_argv[3];~~
	~~extern char **environ;~~
	struct passwd *pw_entry;		struct passwd *pw_entry;

Soma at 03:28, 30 September 2022

2022-09-30T03:28:05Z

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	'''This assignment is ~~still being developed~~.'''		'''This assignment is not yet finalized.'''

	Please submit the answers to the following questions via Brightspace by October 11, 2022 by 11:30 AM. There are ?? points in ?? questions.		Please submit the answers to the following questions via Brightspace by October 11, 2022 by 11:30 AM. There are 20 points in 10 questions.

	Submit your answers as a plain text file following [https://homeostasis.scs.carleton.ca/~soma/os-2022f/templates/comp3000-a2-template.txt this template]. Name your answer file "comp3000-assign2-<username>.txt" (where username is your MyCarletonOne username).		Submit your answers as a plain text file following [https://homeostasis.scs.carleton.ca/~soma/os-2022f/templates/comp3000-a2-template.txt this template]. Name your answer file "comp3000-assign2-<username>.txt" (where username is your MyCarletonOne username).

Soma: /* Questions */

2022-09-30T03:26:46Z

Questions

← Older revision		Revision as of 03:26, 30 September 2022
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	#* a file to be opened for standard error (and created if necessary), and		#* a file to be opened for standard error (and created if necessary), and
	#* a program to run (either an absolute path or a program in the current PATH) with zero or more arguments.		#* a program to run (either an absolute path or a program in the current PATH) with zero or more arguments.
	# [2] ~~Does your implementation of~~ "background" ~~in the previous question work~~ with the "become" command? Why ~~or why not~~?		# [2] How can you ensure that the new "background" can be combined with the "become" command? Why does this work?

	==Code==		==Code==

Soma: /* Questions */

2022-09-30T03:16:09Z

Questions

← Older revision		Revision as of 03:16, 30 September 2022
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	#* a file to be opened for standard output (and created if necessary),		#* a file to be opened for standard output (and created if necessary),
	#* a file to be opened for standard error (and created if necessary), and		#* a file to be opened for standard error (and created if necessary), and
	#* a program to run with zero or more arguments.		#* a program to run (either an absolute path or a program in the current PATH) with zero or more arguments.
	# [2] Does your implementation of "background" in the previous question work with the "become" command? Why or why not?		# [2] Does your implementation of "background" in the previous question work with the "become" command? Why or why not?