Difference between revisions of "CSC220 Lab 1 2010"
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<font size="+2">Page under construction!</font> | <font size="+2">Page under construction!</font> | ||
<br \>[[File:UnderConstruction.jpg|300px]] | <br \>[[File:UnderConstruction.jpg|300px]] | ||
− | </center> | + | </center--> |
You can work in pairs on this lab if you wish. Otherwise work individually. | You can work in pairs on this lab if you wish. Otherwise work individually. | ||
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− | * Login to a Linux box around you using your CSC220a account. | + | * Login to a Linux box around you using your CSC220a account. |
+ | * edit the file .bashrc that should already be in your directory: | ||
+ | |||
+ | emacs -nw .bashrc | ||
+ | |||
+ | * add the following two lines at the end of the file: | ||
+ | |||
+ | |||
+ | PS1='[\h]\n[\t] \w\$: ' | ||
+ | PS2='> ' | ||
+ | |||
+ | * Save the file. | ||
+ | * By default, the shell into which you start is the tcsh. Switch to bash by typing the following command at the prompt: | ||
+ | |||
+ | bash | ||
+ | |||
+ | * Verify that your prompt has changed and looks something like this: | ||
+ | |||
+ | [beowulf] | ||
+ | [09:52:24] ~$: | ||
+ | |||
+ | * You are now ready to explore '''bash''' commands... | ||
=Path-Related Questions= | =Path-Related Questions= | ||
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: Figure out a way to get only the entries from this file that represent printers that are in Ford Hall. | : Figure out a way to get only the entries from this file that represent printers that are in Ford Hall. | ||
− | = | + | ='''Filter'''ing Log Files= |
: Open a browser window and load up the following URL: http://maven.smith.edu/~hadoop/log.txt | : Open a browser window and load up the following URL: http://maven.smith.edu/~hadoop/log.txt | ||
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=Pipes= | =Pipes= | ||
+ | |||
+ | ;Question 1 | ||
+ | : How many users have accounts on grendel (or beowulf)? (''Hints: use ls and wc and a pipe'') | ||
+ | |||
+ | |||
+ | ;Question 2 | ||
+ | : Who are the three users who have modified their account most recently? (''Hints: remember the -ltr switches for ls, and pipe the output to the appropriate command that will give you only three lines'') | ||
+ | |||
+ | |||
+ | ;Question 3 | ||
+ | : Same question, but the three who haven't modified (or touched) their account for the longest time? | ||
+ | ;Question 4 | ||
+ | :Who are the users who have modified their account today? (''Hints: today is a unique character pattern... "Sep 13" '') | ||
+ | |||
+ | =More challenging pipes= | ||
* Use emacs to create the following program in your 220a account: [[CSC220 StdoutStderr.py | stdouterr.py]] | * Use emacs to create the following program in your 220a account: [[CSC220 StdoutStderr.py | stdouterr.py]] | ||
* Make your program executable | * Make your program executable | ||
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./stdouterr.py | ./stdouterr.py | ||
+ | |||
+ | :<font color="magenta">It was observed in the lab that the program might not work when executed as shown above. There are several possibilities for this. One could be that you are using a Windows machine, and when copying-pasting the text of the program in emacs, Windows uses carriage-return (Ascii code 13) to implement the end of lines, while Linux and Macs use line-feed (Ascii code 10) for that purpose. One solution to replace Ascii 13 by Ascii 10 is to use the '''dos2unix''' utility, as follows: | ||
+ | |||
+ | dos2unix stdouterr.py | ||
+ | |||
+ | :You can now try to run stdouterr.py as shown above. | ||
+ | |||
+ | :If that still does not work, you can try the old-fashion way of running python programs: | ||
+ | |||
+ | python stdouterr.py | ||
+ | |||
+ | :and that should work in most cases. Good luck! </font> | ||
+ | |||
:observe the long output. If you observe closely the listing, you will discover that some lines contain error codes, of the form | :observe the long output. If you observe closely the listing, you will discover that some lines contain error codes, of the form | ||
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;Question 2 (tricky) | ;Question 2 (tricky) | ||
+ | : How many lines are output by the program? | ||
+ | |||
+ | |||
+ | ;Question 3 (trickier) | ||
: run the program and use commands that will display only the '''number''' of Error messages | : run the program and use commands that will display only the '''number''' of Error messages | ||
+ | |||
+ | <br /> | ||
+ | <br /> | ||
+ | <br /> | ||
+ | <br /> | ||
+ | <br /> | ||
+ | <br /> | ||
+ | <br /> | ||
+ | <br /> | ||
+ | <br /> | ||
+ | <br /> | ||
+ | <br /> | ||
+ | [[Category:CSC220]][[Category:Labs]][[Category:Bash]] |
Latest revision as of 17:25, 17 November 2010
You can work in pairs on this lab if you wish. Otherwise work individually.
Contents
Login
- Login to a Linux box around you using your CSC220a account.
- edit the file .bashrc that should already be in your directory:
emacs -nw .bashrc
- add the following two lines at the end of the file:
PS1='[\h]\n[\t] \w\$: ' PS2='> '
- Save the file.
- By default, the shell into which you start is the tcsh. Switch to bash by typing the following command at the prompt:
bash
- Verify that your prompt has changed and looks something like this:
[beowulf] [09:52:24] ~$:
- You are now ready to explore bash commands...
Path-Related Questions
- Question 1
- What is the path of your account? In other words, what subdirectories does one have to traverse to reach your account.
- Question 2
- What other subdirectories are at the same height as yours in the directory tree?
- You will notice that all user accounts are in a major directory called Users. The old standard for users on a linux system is to have the users in a directory called home in the root directory.
- Question 3
- You will notice that some user accounts still exist in home. Which are they?
Questions about File-Searching
- With Linux, the name of the printers supported are listed in a file called /etc/printcap. Look at its contents.
- Question 1
- Figure out a way to get only the entries from this file that represent printers that are in Ford Hall.
Filtering Log Files
- Open a browser window and load up the following URL: http://maven.smith.edu/~hadoop/log.txt
- Notice that it is a long log of the output of a research program I have been running recently. It is very long and contains a lot of information: some useful, some not.
- You are going to get a copy of this file into your account. Instead of copying and pasting the text into a file, you are going to use a useful utility called wget. Wget is a Linux utility that allows you to grab Web pages from Web sites, without using a browser.
- Try it:
wget http://maven.smith.edu/~hadoop/log.txt
- Check that the file is in your directory
- Question 1
- How many lines of text does the file contain?
- Question 2
- The second question is to list only the lines that list the real execution time. These lines look like this:
real 23m6.777s
- Go ahead, list the real execution times. What is the shortest time recorded? The longest?
- Question 3
- List not only the real execution times, but also the lines of the form:
processing noTasks = 17240 maxNoTasks = 8, splitSize = 33554432L
- The output should look something like this:
processing noTasks = 862 maxNoTasks = 8 splitSize = 33554432L real 22m11.284s processing noTasks = 862 maxNoTasks = 16 splitSize = 33554432L real 0m13.113s processing noTasks = 1724 maxNoTasks = 8 splitSize = 33554432L real 0m10.891s processing noTasks = 1724 maxNoTasks = 16 splitSize = 33554432L real 0m40.891s processing noTasks = 80 maxNoTasks = 8 splitSize = 33554432L real 2m54.601s
Pipes
- Question 1
- How many users have accounts on grendel (or beowulf)? (Hints: use ls and wc and a pipe)
- Question 2
- Who are the three users who have modified their account most recently? (Hints: remember the -ltr switches for ls, and pipe the output to the appropriate command that will give you only three lines)
- Question 3
- Same question, but the three who haven't modified (or touched) their account for the longest time?
- Question 4
- Who are the users who have modified their account today? (Hints: today is a unique character pattern... "Sep 13" )
More challenging pipes
- Use emacs to create the following program in your 220a account: stdouterr.py
- Make your program executable
chmod +x stdouterr.py
- run your program
./stdouterr.py
- It was observed in the lab that the program might not work when executed as shown above. There are several possibilities for this. One could be that you are using a Windows machine, and when copying-pasting the text of the program in emacs, Windows uses carriage-return (Ascii code 13) to implement the end of lines, while Linux and Macs use line-feed (Ascii code 10) for that purpose. One solution to replace Ascii 13 by Ascii 10 is to use the dos2unix utility, as follows:
dos2unix stdouterr.py
- You can now try to run stdouterr.py as shown above.
- If that still does not work, you can try the old-fashion way of running python programs:
python stdouterr.py
- and that should work in most cases. Good luck!
- observe the long output. If you observe closely the listing, you will discover that some lines contain error codes, of the form
Error 404: blue screen alert!
- Question 1
- run the program and filter its output so that you see only the lines containing error messages
- Question 2 (tricky)
- How many lines are output by the program?
- Question 3 (trickier)
- run the program and use commands that will display only the number of Error messages