Agenda Administrative 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

Administrative issues Call me if you don’t understand an assignment, procedure, or just need a pointer ( ).

Link of the week APA Writing Style APA Style writing guidelines will be utilized for all lab assignment reports. APA Style Sixth Edition APA Style Writing Workshop learning-center/academic-support/workshops.html Grading will focus mainly on capitalization, punctuation, grammar, and citation.

Link of the week Linux 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. help/73994-system-commands-not-working-unless- sbin.html

Course expected outcome Weeks 2 and 3 Upon 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

UNIX Operating System What 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.

UNIX Operating System CLI Benefits Manipulate textual data Quick customization of data allows engineers the abilityto change data to another form Excellent for filtering data on systems Commands are rich, expressive, flexible, and powerful GUI Benefits Reduces data overload Simple filtering and manipulation of the data Excellent for displaying trends in data

UNIX Operating System Customizing the UNIX Shell The 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.

UNIX Operating System FeatureFunctionshcshksh Job controlAllows processes to be executed in the background NoYes History substitutionAllows previous commands to be saved, edited, and reused NoYes File name completionAllows automatic completion of partially typed file name NoYes Command line editingAllows the use of an editor to modify the command line text No Yes Command aliasingAllows users to rename commands NoYes

UNIX Operating System Changing shells It 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 renaming Both 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’

UNIX Operating System File name completion If 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 substitution Both 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.

UNIX Operating System Set ksh history command size HISTSIZE=60; export HISTSIZE Set csh history command size set history=70 Retrieve commands using C Shell Recall the last command !! Recall the command number nine !9

UNIX Operating System UNIX File System A 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.

UNIX Operating System

How a UNIX file system functions Every 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.

UNIX Operating System Types of File and Directory Access AccessFile MeaningDirectory Meaning rView file contentsSearch directory contents wAlter file contentsAlter directory contents xRun executable fileMake your current directory -rwx Owner (columns 2-4) 700 ( ) ----rwx--- Group (columns 5-7) 070 ( ) rwx Other (columns 8-10) 007 ( )

UNIX Operating System File Descriptors A 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.

UNIX Operating System

wc `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

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.

UNIX Operating System Character Action >Redirect standard output >&Redirect standard output and standard error >>&Append standard output and standard error <Redirect standard input

UNIX Operating System Shell 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)

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

UNIX Operating System Pipe command

UNIX Operating System What 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.

UNIX Operating System What is shared memory look like?

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.

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.

UNIX Operating System Introduction to Perl Perl - Practical Extraction and Report Language Originally 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

UNIX Operating System Perl’s range of flexibility System administration Web development Network programming GUI development Major features Procedural Programming Sequence or unstructured statements Includes routines, subroutines, methods, or functions Object Oriented Programming Module uses “objects” and their interactions to design applications and computer programs.

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.

UNIX Operating System Perl language Perl 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.

UNIX Operating System Scope of a Perl variable The 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.

UNIX Operating System Variable and constant A 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.

UNIX Operating System AWK and Perl The 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.

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.

UNIX Operating System Points of interest who | sort > /tmp/test_file.txt The output of the who command is piped to the sort 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.

UNIX Operating System Points 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.

UNIX Operating System Demonstrate 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 Case #2:./srch.sh 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.

UNIX Operating System Moving Around in UNIX more history who –r uname –n cat chgrp chown hostname mv kill

Break-out problems $ARGV[0] 3. filter 4. unless 5. $NUMBER 6. exit 1 7. $ARGV[1] 8. % (%directory) 9. $ ($quote) 11. Regular expressions 12. tr [a-z] [A-Z] /tmp/foo

Hands-On-Information Lab Assignment 2-1, Simple Shell Scripting, due May 18, Lab Assignment 3-1, Advanced Scripting, due May 25, 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.

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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