Introduction to Unix CS 21

1
Introduction to Unix CS 21

• Lecture 14

2
Lecture Overview

• Lab Questions
• Backup schemes
• Using tar to archive
• Printing in Unix
• lpr
• lpq
• Lprm
• Quiz 2

3
Bash Shell Scripting Clarifications

• /bin/bash
• Must be the absolute first line in your script,
  otherwise it is meaningless
• Put before your name, and before anything else
• will start a comment, so put in front of your
  name
• Always run your scripts to verify what they are
  doing before you turn them in

4
Take Home Assignment Clarifications

• This is longer than all other programs so far, so
  if you havent started yet, start ASAP
• Due at the beginning of lab on Thursday (600 pm)
• Hints
• Awk can be treated like just another bash
  program, so you can make calls and awk programs
  inside your bash shell script
• Indent for readibility (Comment for
  understandability)

5
Once A File Is Gone, Its Gone

• The only way to prevent data loss is to keep a
  recent copy somewhere safe
• Of course, the entire hard drive could fail, so
  to be safer you need it in multiple locations
• Other hard drives
• Backup tapes

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Our System - RAID

• Redundant array of independent disks
• Every hour a process checks and stores away any
  difference in your directories and files
• Places these files in the .snapshot direcotry
• Located on one or more other drives

7
Tape Archive - tar

• Designed to store files onto a tape device
• Now used for for storing and collecting files
  anywhere
• Creates and maintains archives
• Commonly seen as XXXX.tar files
• Usage tar FLAGS FILES

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Common Flags

• -c
• Create an archive
• -f
• Specify file
• -x
• Extract an archive
• -t
• List an archive

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Creating A tar Archive

• tar cf backup.tar FILES
• tar c FILES gt backup.tar
• As always, if you use file redirection be careful
• Easy to overwrite

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Example
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Listing A tar Archive

• tar tf backup.tar
• tar t lt backup.tar
• Will simply print out a list of all files located
  in that tar archive without changing them

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Example
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Extracting A tar Archive

• tar x lt backup.tar
• tar xf backup.tar
• Will create all of the files in their respective
  directories
• Will overwrite any files that are there already,
  so be carefule

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Example
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Automatically Compressing A tar Archive

• -Z
• Runs zip automatically on all files
• -z
• Runs gzip automatically on all files
• Example
• tar czf compressed.tar.gz .txt

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The Most Common Usage

• Tarfile.tar.gz
• Referred to as a tarball
• Almost all Unix programs and packages are
  available in this form
• To extract them
• tar xzvf tarball.tar.gz

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Example
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Basic Printing In Unix

• The printers expect to be given a .ps file
• Postscript
• Other formats may or may not work or may come out
  ugly
• Pdf (Adobe Acrobat format)
• Ascii (Straight text)

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lpr

• Directly feed a printer a ps file to print
• Usage lpr FLAGS toPrint.ps
• Most common flag
• -Pname
• Specifies the name of the printer to send it to
• Default is located in /etc/cups/lpoptions

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lpq

• Prints out a list of all jobs waiting to be
  printed from a specific printer
• Each job has an associated job ID
• Usage lpq FLAGS
• Most common usages
• lpq
• lpq -Pname

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Poor Example
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lprm

• Used to remove jobs from the queue
• Usage lprm FLAGS jobID
• Example
• lprm Pname 23

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Always Remove Your Print Jobs That Dont Print!

• Sometimes, the printers dont work and people
  send jobs to the printers without knowing it
• These jobs hang around until the printers start
  working again, and then everything gets printed
• Your work could print out when youre not there
  and someone else could take it

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a2ps

• Convert ASCII files into the .ps format
• Usage a2ps FLAGS asciiFile
• Examples
• a2ps o printMe.ps asciiFile
• a2ps Pname asciiFile

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pdf2ps

• Converts Pdf format files into .ps files
• Usage pdf2ps input.pdf output.ps

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Viewing ps, pdf, And Other Files

• gs
• Ghostscript
• A basic ps and pdf viewer
• gv
• Ghostview
• A more user friendly ps and pdf viewer
• xpdf
• A pdf viewer

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Next Time

• Perl Programming Basics
• Syntax
• When would you use perl?

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Quiz 2

• Good Luck