Agenda
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Transcript of Agenda
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AgendaAdministrative Issues Link of the Week Review Week Two Information This Week’s Expected Outcomes Next Lab Assignment Break-Out Problems Upcoming Deadlines Lab Assistance, Questions, and Answers
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Administrative issuesCall me if you don’t understand an assignment, procedure, or just need a pointer (614.519.5853).
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Link of the weekAPA Writing Style
APA Style writing guidelines will be utilized for all lab assignment reports .
APA Style Sixth Editionhttp://www.apastyle.org/learn/APA Style Writing Workshophttp://www.franklin.edu/student-services/student-learning-center/academic-support/workshops.html
Grading will focus mainly on capitalization, punctuation, grammar, and citation.
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Link of the weekLinux Forums Web Site
This web site allows individuals to post questions about Fedora Linux and Redhat Linux. The people that maintain this site are knowledgeable users of these operating systems. If your experiencing problems with commands or just want to learn more about these systems, you can find this type of information at this site.
http://www.linuxforums.org/forum/redhat-fedora-linux-help/73994-system-commands-not-working-unless-sbin.html
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Course expected outcome Weeks 2 and 3Upon successful completion of this module, the student
will be able to:Create scripts using shell/Perl variables and program
control flow. Use redirection and pipes to combine scripts and
executables. Use man page system and find script tools. Discuss Perl Language
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UNIX Operating SystemWhat is the next user interface going to be?
The textual (command line) and the visual (graphical user) interfaces are the two most common modalities used to support engineers in network and system administration positions. The command line interface is recognized as the first generation and the graphical user interface is considered the second generation. Currently, research is trying to determine the next best interface. The command line interface is known as, “under the hood” method of interacting with the operating system.
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UNIX Operating SystemCLI Benefits
Manipulate textual dataQuick customization of data allows engineers the abilityto change data to another formExcellent for filtering data on systemsCommands are rich, expressive, flexible, and powerful
GUI Benefits
Reduces data overloadSimple filtering and manipulation of the dataExcellent for displaying trends in data
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UNIX Operating SystemCustomizing the UNIX ShellThe UNIX shell is a user program that is executed by the kernel when you log in to your terminal. As previously displayed, UNIX systems usually provide several shells for users to select from. The most common shells are the Bourne Shell (sh), the C Shell (csh) and the Korn Shell (ksh). Each of the shells listed vary in some way for specific reasons.
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UNIX Operating SystemFeature Function sh csh ksh
Job control Allows processes to be executed in the background
No Yes Yes
History substitution Allows previous commands to be saved, edited, and reused
No Yes Yes
File name completion Allows automatic completion of partially typed file name
No Yes Yes
Command line editing Allows the use of an editor to modify the command line text
No No Yes
Command aliasing Allows users to rename commands
No Yes Yes
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UNIX Operating SystemChanging shellsIt is possible to invoke a different shell, while within another shell, you just type the name of the shell you want to execute, ksh, csh, or sh.Command renamingBoth ksh and csh provide command name aliasing, which allows you to change a command name. Command aliasing can save you time and keystrokes by renaming frequently issued long commands. Tow pieces of information are needed. The command you want to alias, and the alias you want to use to refer to it.
alias g=‘grep’
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UNIX Operating SystemFile name completionIf you dislike lengthy typing, csh and ksh provide a feature the allows you to type partial file names. By typing a partial file name and pressing the ESCAPE key once for csh and twice for ksh, you can retrieve the file.If the beginning characters for a file are entered and the file doe not exist, the shell will beep at you.Command history substitutionBoth ksh and csh maintain an ordered list of commands that you issued, allowing them to be retrieved from the list. Typing the history command will displayed the list of previous commands issued.
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UNIX Operating SystemSet ksh history command size
HISTSIZE=60; export HISTSIZE
Set csh history command sizeset history=70
Retrieve commands using C ShellRecall the last command
!!Recall the command number nine
!9
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UNIX Operating SystemUNIX File SystemA disk drive is a device that stores data by making electrical imprints on a magnetic surface, optical, or mechanical changes to a surface layer of one or more rotating disks.A hard disk consists of one or more circular aluminum platters of which either or both surfaces are coated with a magnetic substance used for recording the data. For each surface, there is a read-write head that examines or alters the recorded data. The platters rotate on a common axis; typical rotation speed is 5400 or 7200 rotations per minute, although high-performance hard disks have higher speeds and older disks may have lower speeds. The heads move along the radius of the platters; this movement combined with the rotation of the platters allows the head to access all parts of the surfaces.
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UNIX Operating System
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UNIX Operating System
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UNIX Operating SystemHow a UNIX file system functionsEvery item in a UNIX file system can be identified to belong to one of the four types: Ordinary files contain text, data, or program information. They cannot contain
another file or directory. They can be viewed as a one-dimensional array. Directory contain files, and other directories. A directory is a file that has one
line for each item contained within the directory. Each line in a directory file contains the name of the item, and a numeric reference to the location of the item. The numerical reference is called, i-node, which will be discussed at a later time.
Link is a pointer to another file. As a review, a directory is a list of the names and i-numbers of files. A directory entry can be a Hard Link or a Symbolic link. Both of these topics will be addressed at a later time.
Special files are files representing input/output (i/o) devices. A special file can be a printer, a disk drive, or a terminal. Because UNIX treats all such devices as a file, it achieves a greater degree of compatibility between i/o devices and i/o of ordinary files, providing more efficient use of software.
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UNIX Operating SystemTypes of File and Directory AccessAccess File Meaning Directory Meaning r View file contents Search directory contents
w Alter file contents Alter directory contents
x Run executable file Make your current directory-rwx------ Owner (columns 2-4) 700 (111000000)----rwx--- Group (columns 5-7) 070 (000111000)-------rwx Other (columns 8-10) 007 (000000111)
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UNIX Operating SystemFile DescriptorsA file descriptor is generally an index for an entry in a kernel-resident data structure that contains information on all open files. Each process on the system has its own file descriptor table. A user application passes the abstract key to the kernel through a system call, and the kernel accesses the file for the application.
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UNIX Operating System
Keyboard
DisplayScreen
Program
#0 stdin
#1 stdout
#2 stderr
File Descriptor
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UNIX Operating Systemwc `ls` commands
The word count (wc) command reads either standard input or a list of files and generates one or more of the following statistics: newline count, word count, and byte count.A snippit of output from the wc –l `ls` command:
19 xyz.sh 2 zombie 24 zombie.c 9890 total
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UNIX Operating System
Shell and Programs Access
To run a shell script, you will need read (r) and execute (x) access (r-x). The read access mode is a binary 4. The execute access mode is a binary 1.
To run a binary executable program, you will need execute (x) access (--x). The execute access mode is a binary 1.
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UNIX Operating System
Character Action> Redirect standard output>& Redirect standard output and standard error>>& Append standard output and standard error< Redirect standard input
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UNIX Operating SystemShell redirect
ls –a > /tmp/output 2>&1 (stderr redirected to stdout) > is equivalent to 1> (stdout (write) redirect
symbol))< is equivalent to <0 (stdin (read) redirect
symbol)
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UNIX Operating System
Pipe command (command1 | command2)
Command2 does not start executing until command1 has finished, and a sufficiently large scratch file is required to hold the intermediate results as well as whatever work space each task required.
command1 > tempfile command2 < tempfile rm tempfile
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UNIX Operating System
Pipe command
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UNIX Operating SystemWhat is a data structure?
A data structure is a specific way of storing and organizing data in a computer so that it can be accessed with high efficiently. Data structures can be used as a single place for storing unrelated information. A data structure is a particular way of storing and organizing data in a computer so that it can be used efficiently.Different kinds of data structures are suited to different kinds of applications, and some are highly specialized to specific tasks.
Some common data structures:array, hash table, linked list, queue, and stack.
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UNIX Operating SystemWhat is shared memory look like?
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UNIX Operating System
What is a regular expression?A regular expression (abbreviated regex or
regexp) is a sequence of characters that forms a search pattern, mainly for use in pattern matching with strings, or string matching, i.e. "find and replace"-like operations. The concept arose in the 1950s, when the American mathematician Stephen Kleene formalized the description of a regular language, and came into common use with the Unix text processing utilities ed, an editor, and grep (global regular expression print), a filter.
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UNIX Operating System
Shell and Programs Access
To run a shell script, you will need read (r) and execute (x) access (r-x). The read access mode is a binary 4. The execute access mode is a binary 1.
To run a binary executable program, you will need execute (x) access (--x). The execute access mode is a binary 1.
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UNIX Operating System
Introduction to PerlPerl - Practical Extraction and Report LanguageOriginally developed by Larry Wall, a linguist.Perl is 21 years old and Perl 5 is 14 years old.
Perl is a simple language- Compiles and executes like a shell script or a batch file- Perl doesn’t impose special growth limitations on arrays and data strings- Perl is a composite of C, AWK, and Basic- Originally developed to process text and automating tasks
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UNIX Operating SystemPerl’s range of flexibility System administrationWeb developmentNetwork programmingGUI developmentMajor featuresProcedural Programming
Sequence or unstructured statementsIncludes routines, subroutines, methods, or functions
Object Oriented ProgrammingModule uses “objects” and their interactions to design applications and computer programs.
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UNIX Operating System
Major features (continued)- Powerful built-in support for text
processing - Large collection of third-party
modules.Variable
A variable is a storage location that can hold any of various kinds of value, as a program sees fit. This storage location is an abstract area known as namespaces.
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UNIX Operating System
Perl languagePerl is a free-form language, but is not free of
form. Perl is a free-form language in which you can put spaces, tabs, and new lines anywhere you like, except where they aren’t allowed.
Whitespace cannot be placed within a token. A token is a sequence of characters with a unit of meaning, like a word in the English language. But unlike the typical word, a token can contain other letters and characters as long as the are kept together.
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UNIX Operating System
Scope of a Perl variableThe scope of a variable means how far away you
can see a variable, looking through one. Perl has two visible mechanisms.Dynamic scoping of local variables, meaning that the
rest of the block, and any subroutines that are called by the rest of the block, can see the variables that are local to the block.
Lexical scoping of “my” variables, meaning that the rest of the block can see the variable, but other subroutines called by the block cannot see the variable.
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UNIX Operating System
Variable and constantA variable is a named object that resides in RAM
memory and is capable of being examined and modified. A variable is used to hold information critical to the operation in an embedded system.
A constant is a named object that resides in memory (usually in ROM) and is only capable of being examined.
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UNIX Operating System
AWK and PerlThe AWK utility is an interpreted programming
language typically used as a data extraction and reporting tool. It is a standard feature of most Unix-like operating systems.
AWK was created at Bell Labs in the 1970s, and its name is derived from the family names of its authors – Alfred Aho, Peter Weinberger, and Brian Kernighan.
The power, terseness, and limits of early AWK programs inspired Larry Wall to write Perl just as a new, more powerful POSIX AWK and gawk (GNU AWK) were being defined.
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UNIX Operating System
Why is awk language so important?
Awk language is an excellent filter and report writer. Many UNIX utilities generate rows and columns of information. Awk is an excellent tool for processing rows and columns, and it is easier to use awk than other conventional programming languages. Perl recognized the importance of awk, so it was included and enhanced in Perl.
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UNIX Operating SystemPoints of interestwho | sort > /tmp/test_file.txt
The output of the who command is piped to thesort function and written in ascending order in the/tmp/test_file.txt file. The “who” and “sort” commands both write and read an intermediate file.
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UNIX Operating SystemPoints of interest
Knoppix software was designed to be used as a Live CD because of specific features that make it’s performance and stability very suitable. It has been noted in several articles that Knoppix works best from a Live CD. Knoppix enthusiasts have attempted to install this software on a hard disk and encountered problems in the process. These problems are most pronounced when installing updates and new software.
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UNIX Operating SystemDemonstrate
The Advanced Scripting lab assignment requires two shell scripts to be written. srch.sh srchfile.sh
Execution of srch.sh and srchfile.sh Case #1: ./srch.sh <pattern> <file name / directory
name>Case #2: ./srch.sh <pattern> <.>The srch.sh script will call the srchfile.sh script to perform a specific task. The srchfile.sh searches for a file with a pattern and outputs the matching information to standard output. After all directory entries have been read, control is returned to the main script, srch.sh.
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UNIX Operating SystemMoving Around in UNIX
morehistorywho –runame –ncatchgrpchownhostnamemvkill
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Break-out problems
1. scalar@ARGV2. $ARGV[0]3. filter4. unless5. $NUMBER6. exit 17. $ARGV[1]8. % (%directory)9. $ ($quote)10. @ (@names)11. Regular expressions12. tr [a-z] [A-Z] < foobar > /tmp/foo
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Hands-On-InformationLab Assignment 2-1, Simple Shell Scripting, due
May 18, 2014.Lab Assignment 3-1, Advanced Scripting, due May
25, 2014.Read Chapters 3 and 4 in Essential System
Administration text.Read Module Two listed under the course Web site.Everyone should have received a Shell Quick
Reference document and script logic for Lab Assignment 2-1.
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After Class Assistance
Questions?Comments?Concerns?
After each Franklin Live session, I will remain on the session to provide assistance unless otherwise indicated.
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Lab assistance, questions, and chat time