Operating Systems 2021F: Tutorial 3 - Revision history

Soma at 20:04, 9 October 2021

2021-10-09T20:04:35Z

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	In this tutorial you will be experimenting with and extending [~~http~~://homeostasis.scs.carleton.ca/~soma/os-2019f/code/3000shell.c 3000shell.c] (listed below).		In this tutorial you will be experimenting with and extending [https://homeostasis.scs.carleton.ca/~soma/os-2019f/code/3000shell.c 3000shell.c] (listed below).

	'''Make sure you use the original code from 3000shell for each question.'''		'''Make sure you use the original code from 3000shell for each question.'''

Soma: /* Getting Started */

2021-10-09T20:04:11Z

Getting Started

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	==Getting Started==		==Getting Started==

	You should download [~~http~~://homeostasis.scs.carleton.ca/~soma/os-2019f/code/3000shell.c 3000shell.c] on your openstack instance (or a Ubuntu Linux 21.04 system or similar). Compile it using the command		You should download [https://homeostasis.scs.carleton.ca/~soma/os-2019f/code/3000shell.c 3000shell.c] on your openstack instance (or a Ubuntu Linux 21.04 system or similar). Compile it using the command
	gcc -O -g -Wall 3000shell.c -o 3000shell		gcc -O -g -Wall 3000shell.c -o 3000shell

Soma: /* 3000shell.c */

2021-10-09T20:04:01Z

3000shell.c

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	==Code==		==Code==

	===3000shell.c===		===[https://homeostasis.scs.carleton.ca/~soma/os-2019f/code/3000shell.c 3000shell.c]===

	<syntaxhighlight lang="c" line>		<syntaxhighlight lang="c" line>

Soma: /* Standard I/O */

2021-10-02T01:21:44Z

Standard I/O

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	When you ssh to a system interactively, the remote ssh process uses a pseudo tty to connect network I/O with the programs you run at the command line. In this context you can thus think of ssh (plus a pseudo tty) as an adaptor that converts network traffic into terminal-like I/O.		When you ssh to a system interactively, the remote ssh process uses a pseudo tty to connect network I/O with the programs you run at the command line. In this context you can thus think of ssh (plus a pseudo tty) as an adaptor that converts network traffic into terminal-like I/O.

	Standard input, (e.g., /dev/~~stdout~~), output (e.g., /dev/~~stdin~~) and error (/dev/stderr) are just		Standard input, (e.g., /dev/stdin), output (e.g., /dev/stdout) and error (/dev/stderr) are just
	references to file descriptors 0, 1, and 2 for the current process. They can refer to basically any file. If a process is run in a terminal, stdin, stdout, and stderr are set to refer to the terminal's I/O channels via a tty or pts.		references to file descriptors 0, 1, and 2 for the current process. They can refer to basically any file. If a process is run in a terminal, stdin, stdout, and stderr are set to refer to the terminal's I/O channels via a tty or pts.

Soma: /* Standard I/O */

2021-09-27T19:51:34Z

Standard I/O

← Older revision		Revision as of 19:51, 27 September 2021
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	==Standard I/O==		==Standard I/O==

	Recall that the shell is a command interpreter (program). In comparison, a terminal is a device used to enter data into and display data from a computer. It used to be physical - [https://en.wikipedia.org/wiki/Teleprinter teletypes, or "~~tty~~"'s]. Today they are virtual - pseudoterminals, pseudo teletypes, or pts's. /dev/pts/1 is a pts for example. By themselves, a pts does nothing; however, they allow any program to appear as a virtual teletype to any other program. (To learn more, <tt>man ptmx</tt>. However, this goes into more detail than you need for this tutorial.)		Recall that the shell is a command interpreter (program). In comparison, a terminal is a device used to enter data into and display data from a computer. It used to be physical - [https://en.wikipedia.org/wiki/Teleprinter teletypes, or "TTY"'s]. Today they are virtual - pseudoterminals, pseudo teletypes, or pts's. /dev/pts/1 is a pts for example. By themselves, a pts does nothing; however, they allow any program to appear as a virtual teletype to any other program. (To learn more, <tt>man ptmx</tt>. However, this goes into more detail than you need for this tutorial.)

	When you ssh to a system interactively, the remote ssh process uses a pseudo tty to connect network I/O with the programs you run at the command line. In this context you can thus think of ssh (plus a pseudo tty) as an adaptor that converts network traffic into terminal-like I/O.		When you ssh to a system interactively, the remote ssh process uses a pseudo tty to connect network I/O with the programs you run at the command line. In this context you can thus think of ssh (plus a pseudo tty) as an adaptor that converts network traffic into terminal-like I/O.

Soma: /* Standard I/O */

2021-09-27T19:51:10Z

Standard I/O

← Older revision		Revision as of 19:51, 27 September 2021
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	==Standard I/O==		==Standard I/O==

	Recall that the shell is a command interpreter (program). In comparison, a terminal is a device used to enter data into and display data from a computer. It used to be physical - teletypes, or "tty"'s. Today they are virtual - pseudoterminals, pseudo teletypes, or pts's. /dev/pts/1 is a pts for example. By themselves, a pts does nothing; however, they allow any program to appear as a virtual teletype to any other program. (To learn more, <tt>man ptmx</tt>. However, this goes into more detail than you need for this tutorial.)		Recall that the shell is a command interpreter (program). In comparison, a terminal is a device used to enter data into and display data from a computer. It used to be physical - [https://en.wikipedia.org/wiki/Teleprinter teletypes, or "tty"'s]. Today they are virtual - pseudoterminals, pseudo teletypes, or pts's. /dev/pts/1 is a pts for example. By themselves, a pts does nothing; however, they allow any program to appear as a virtual teletype to any other program. (To learn more, <tt>man ptmx</tt>. However, this goes into more detail than you need for this tutorial.)

	When you ssh to a system interactively, the remote ssh process uses a pseudo tty to connect network I/O with the programs you run at the command line. In this context you can thus think of ssh (plus a pseudo tty) as an adaptor that converts network traffic into terminal-like I/O.		When you ssh to a system interactively, the remote ssh process uses a pseudo tty to connect network I/O with the programs you run at the command line. In this context you can thus think of ssh (plus a pseudo tty) as an adaptor that converts network traffic into terminal-like I/O.
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	(This is really good if you have lots of files in a directory.)		(This is really good if you have lots of files in a directory.)

	Part of the magic of UNIX is that it allows problems to be solved by combining multiple programs together. For example, to get a list of unique words in a file, do the following:		Part of the magic of UNIX is that it allows problems to be solved by combining multiple programs together. For example, to get a list of unique words in a file, you can do something like the following:

	tr ' \t' '\n' < file.txt \| tr -d ',.!()?-' \| sort \| uniq \| less		tr ' \t' '\n' < file.txt \| tr -d ',.!()?-' \| sort \| uniq \| less

Soma: /* Tasks/Questions */

2021-09-27T19:37:23Z

Tasks/Questions

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	# Implement redirection of standard error		# Implement redirection of standard error
	# Implement redirection of standard out for plist() (the same as if it was an external command).		# Implement redirection of standard out for plist() (the same as if it was an external command).
	# Implement a built-in 3000kill command that works like the standard kill command.		# Implement a built-in 3000kill command that works like the standard kill command. (What system call/library call is used to send signals?)

	==Code==		==Code==

Soma: /* Standard I/O */

2021-09-27T19:36:05Z

Standard I/O

← Older revision		Revision as of 19:36, 27 September 2021
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	Part of the magic of UNIX is that it allows problems to be solved by combining multiple programs together. For example, to get a list of unique words in a file, do the following:		Part of the magic of UNIX is that it allows problems to be solved by combining multiple programs together. For example, to get a list of unique words in a file, do the following:

			tr ' \t' '\n' < file.txt \| tr -d ',.!()?-' \| sort \| uniq \| less

	In summary, shells run in terminals, and the terminal interface is implemented by teletype-like devices, either a "tty" or "pts" device. Standard in, out, and error are abstractions for interactions with such terminals or, with I/O redirection, other arbitrary files.		In summary, shells run in terminals, and the terminal interface is implemented by teletype-like devices, either a "tty" or "pts" device. Standard in, out, and error are abstractions for interactions with such terminals or, with I/O redirection, other arbitrary files.

Soma: /* Standard I/O */

2021-09-27T19:30:30Z

Standard I/O

← Older revision		Revision as of 19:30, 27 September 2021
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	When you ssh to a system interactively, the remote ssh process uses a pseudo tty to connect network I/O with the programs you run at the command line. In this context you can thus think of ssh (plus a pseudo tty) as an adaptor that converts network traffic into terminal-like I/O.		When you ssh to a system interactively, the remote ssh process uses a pseudo tty to connect network I/O with the programs you run at the command line. In this context you can thus think of ssh (plus a pseudo tty) as an adaptor that converts network traffic into terminal-like I/O.

	Standard ~~output~~ (e.g., /dev/stdout), ~~input~~ (e.g., /dev/stdin) and error (/dev/stderr) are just		Standard input, (e.g., /dev/stdout), output (e.g., /dev/stdin) and error (/dev/stderr) are just
	references to file descriptors 0, 1, and 2 for the current process. They can refer to basically any file. If a process is run in a terminal, stdin, stdout, and stderr are set to refer to the terminal's I/O channels via a tty or pts.		references to file descriptors 0, 1, and 2 for the current process. They can refer to basically any file. If a process is run in a terminal, stdin, stdout, and stderr are set to refer to the terminal's I/O channels via a tty or pts.

			Shells provide easy interfaces for changing these file descriptors. For example:

			ls > ls.log

			Will redirect ls's standard output to the file ls.log. Similarly,

			bc -l < math.txt

			will take math input from /tmp/math.txt and output it to the current terminal. We can also use the pipe operator to direct the standard output of one program to the standard input of another:

			ls -l \| less

			(This is really good if you have lots of files in a directory.)

			Part of the magic of UNIX is that it allows problems to be solved by combining multiple programs together. For example, to get a list of unique words in a file, do the following:



	In summary, shells run in terminals, and the terminal interface is implemented by teletype-like devices, either a "tty" or "pts" device. Standard in, out, and error are abstractions for interactions with such terminals or, with I/O redirection, other arbitrary files.		In summary, shells run in terminals, and the terminal interface is implemented by teletype-like devices, either a "tty" or "pts" device. Standard in, out, and error are abstractions for interactions with such terminals or, with I/O redirection, other arbitrary files.

Soma at 19:24, 27 September 2021

2021-09-27T19:24:21Z

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 You should download [http://homeostasis.scs.carleton.ca/~soma/os-2019f/code/3000shell.c 3000shell.c] on your openstack instance (or a Ubuntu Linux 21.04 system or similar).  Compile it using the command
   gcc -O -g -Wall 3000shell.c -o 3000shell
 ==Tasks/Questions==