Linux project | Computer Science homework help

The Korn Shell is the UNIX shell (command execution program, often called a command interpreter) that was developed by David Korn of Bell Labs as a comprehensive, combined version of other major UNIX shells. Incorporating all the features of the C shell (csh) and the Tab C-shell (tcsh) with the script language features similar to that of the Bourne Shell, the Korn Shell is considered the most efficient shell. Korn, Bourne, and C are the 3 most commonly used UNIX shells. You will be using the Korn Shell (ksh) for this project in which you will be writing shell script files.

1.      Begin by executing the following command from a terminal session in your Ubuntu system:

sudo  apt-get  install  ksh  <Enter>

You will immediately be asked to enter your password (csci345). This will install the Korn shell into your Ubuntu system on your PC or Mac for use in this project. Simply type ksh and <Enter> to go into the Korn Shell (your system prompt will change to $ only) and then enter CTRL-D to exit out of it (your default system prompt of [email protected]:~$ will re-appear).

As you go through this exercise and start writing shell scripts, you will learn some additional troubleshooting tips to help you navigate through the Korn Shell (ksh).

Keep track of some of these tips (5 of them) and put them into a Word document in a list format with explanations (at least 150 words in current APA format). Make sure that these are different from those mentioned in the textbook. 

2.      Do some research on what the Korn Shell is about and what it has to offer. Provide some basic information (3–5 key points) in a short report (at least 150 words in current APA format) and compile it into the same Word document as above and submit it with this project. Also, provide 5–7 positive features of the Korn Shell (ksh) in the same report (at least 150 words in current APA format) in a list. Below are 3 websites that can assist you in this effort. You will need at least 2 external references for this short report (in addition to your textbook):

– http://kornshell.com/
– http://www.dartmouth.edu/~rc/classes/ksh/print_pages.shtml
– http://www.bolthole.com/solaris/ksh.html

There are many other websites out there that will give you additional help, if needed. Take a look at the ksh shell script below. There are 3 versions of essentially the same program, which is a wrapper to edit a file under SCCS version control. The basic task is to use the sccs command to “check out” a file under version control and then automatically edit the file. The script will then be used by users who may not be particularly advanced UNIX users. Hence, the need for a wrapper script. While the basic functionality is the same across all versions, the differences in safety and usability between the first version and the last (4th) version are worth noting. The first one is extremely bad: it would be written by someone who has just picked up a book on shell scripting and has decided, “I’m a programmer now.”

#!/bin/ksh

sccs edit $1

if [ “$EDITOR” = “” ] ; then

            EDITOR=vi

fi

$EDITOR $1

This version makes somewhat of an attempt to be user-friendly by having a check for an environmental variable EDITOR setting and using it, if available; however, there are no comments, no error checking, and no help for the user at all. The second one is an improvement, showing some consideration to potential users by having safety checks.

#!/bin/ksh

# Author: Name Here

if [ $# -lt 1 ] ; then

            print “This program will check out a file, or files, with sccs”

            exit 1

fi

# set EDITOR var to “vi” if not already set

EDITOR=${EDITOR:-vi}

sccs edit [email protected]

$EDITOR [email protected]

This is a step above the prior version. It accepts multiple files as potential arguments. It is always nice to be flexible about the number of files your scripts can handle. It also has a usage message if the script is called without arguments. Plus, it is always a good idea to put your name in as well. Unfortunately, there is still quite a bit lacking as you can tell by comparing it to the next version. The third one is a good, solid version; it is a positive role model for your scripts.

#!/bin/ksh

# SCCS editing wrapper, version 0.3

#  Author – Sys Admin

#  Usage: see usage() function, below

usage(){

       print sedit – a wrapper to edit files under SCCS

       print “usage: sedit file {file2 …}”

}

# Set EDITOR var to “vi” if not already set to something

EDITOR=${EDITOR:-vi}

# Could already be in path, but it doesn’t hurt to add it again.

# adjust as needed,  if your sccs lives somewhere else

SCCSBIN=/usr/ccs/bin

if [ ! -x $SCCSBIN/sccs ] ; then

       print ERROR: sccs not installed on this machine. Cannot continue.

       usage

       exit 1

fi

PATH=$SCCSBIN:$PATH

if [ $# -lt 1 ] ; then

       usage

       print ERROR: no files specified

       exit 1

fi

# Yes, I could use “sccs edit [email protected]” and check for a single error, but # this approach allows for finer error reporting

for f in [email protected] ; do

       sccs edit $f

       if [ $? -ne 0 ] ; then

                      print ERROR checking out file $f

                      if [ “$filelist” != “” ] ; then

                                     print “Have checked out $filelist”

                      fi

                      exit 1

       fi

       filelist=”$filelist $f”

done

$EDITOR $filelist

if [ $? -ne 0 ] ; then

       print ERROR: $EDITOR returned error status

       exit 1

fi

Here are some nice things to note with this script:

·         Sets special variables at the top of the script in a unified place;

·         Paranoid checks about EVERYTHING;

·         Returns an error status from the script on non-clean exit condition (“exit 1” vs. “exit”); and

·         Use of comments. Not only does he/she specify what he/she is doing, he/she clarifies what she/she is NOT doing and why.

3.      Now that you have the Korn Shell (ksh) installed and have learned more about the language itself, it is time to do some programming:

a.       Write a Korn shell script that accepts exactly 1 command line argument that must be a positive integer. The script will print a comma separated list of integers, all on the same line, starting with the initial command line value and decreasing it by one-to-one. The last printed value must not be followed by a comma. Do not write this script to be executed interactively.

Requirements:

The script must be to handle the following error situations:

1.      Incorrect number of arguments and

2.      Non-positive arguments.

The script file name must be: printnum.sh

The script permissions must be 705 (show in your Word document).

Sample Output (provide yours in same Word document)

Sunny Day Scenarios:

[email protected]:~$  sh printnum.sh 3

3, 2, 1

[email protected]:~$

[email protected]:~$  sh printnum.sh 10

10, 9, 8, 7, 6, 5, 4, 3, 2, 1

[email protected]:~$

Rainy Day Scenarios:

[email protected]:~$  sh printnum.sh

error: program must be executed with 1 argument. usage: printnum.sh value (where value >= 1)

[email protected]:~$  sh printnum.sh 2 5

error: program must be executed with 1 argument. usage: printnum.sh value (where value >= 1)

[email protected]:~$  sh printnum.sh -1

error: argument must be a positive number. usage: printnum.sh value (where value >= 1)

Add at least 2 more scenarios in your Word document.

b.      Write a Korn shell script that will determine which file in a directory has the maximum number of lines (this may be different than the file that has the maximum number of bytes). After determining the file with the maximum number of lines, the script will print out the name of the file and the number of lines. The script must only focus on files and ignore subdirectories. The command wc may be helpful. Do not write this script to be executed interactively.

Requirements:

·         The script must allow either no arguments or 1 argument.

1.      If zero arguments are specified, the script by default will examine the files in the current directory.

2.      If 1 argument is specified, the argument must be the name of a directory. The script will then examine the files in the specified directory.

The script must be able to handle the following error conditions:

1.      More than 1 argument is specified.

2.      The specified argument is not a directory.

The script file name must be: maxlines.sh

The script permissions should be 705

Sample Output (provide yours in same Word document)

Sunny Day Scenarios(Note: output depends on current directory and may not match the values below):

[email protected]:~$  sh maxlines.sh

File maxlines.sh has maximum number lines (36 lines).

[email protected]:~$ sh maxlines.sh  /etc

File mime.types has the maximum lines with 827 lines.

Rainy Day Scenarios:

[email protected]:~$ sh maxlines.sh junk

error: argument must be a directory usage: maxlines.sh [directory]

[email protected]:~$ sh maxlines.sh junk trash

error: can only use 0 or 1 arguments. usage: maxlines.sh [directory]

Add at least 2 more scenarios in your Word document.

c.       Create a search utility by writing 2 Korn Shell scripts named srchfile.sh and srch.sh, respectively. The script srchfile.sh will list all occurrences of a string found in a file. The script srch.sh will list all occurrences of a string in a file or all files in a specified directory. Actually, srch.sh will use the script srchfile.sh as if it were just another UNIX command to perform the actual search in a file. In other words, the script srch.sh needs to be able to use the script srchfile.sh. Therefore, this assignment recommends that the first script created be the srchfile.sh script. The script srch.sh calls the srchfile.sh script.

Requirements:

Part 1

Description.

The shell script srchfile.sh must accept 2 command line arguments.

1.      The script shall first print the name of the file being searched.

2.      If there are one more instances of the string in the file, the script shall print each line that contains the matching string, along with the line number of the file.

You may use the UNIX command grep in your script to do the actual search. In fact, grep can even print the line number if used with the appropriate option (see man page for grep).

If the user enters more or fewer than the required number of arguments, the script shall produce an error message and stop.

The first argument shall represent the string to be searched.

The second argument shall represent the name of the file to be searched. If the second argument is not a file, the script shall produce an error message and stop.

The script file name must be: srchfile.sh.

The script permissions must be 705

Sample Output (provide yours in same Word document)

In the Sunny Day Scenario, the srchfile.sh script is invoked searching for string root pattern in file passwd in the /etc directory:

[email protected]:~$  sh srchfile.sh root /etc/passwd

—— File = /etc/passwd ——

1:root:x:0:0:root:/root:/bin/bash

In the Rainy Day Scenario, script srchfile.sh is invoked with only 1 command line argument:

[email protected]:~$  sh srchfile.sh xxxx

            error: must provide 2 arguments

            usage: sh srchfile.sh search-pattern file

In the Rainy Day Scenario, script srchfile.sh is invoked with second command line argument /etc., which is a directory rather than a file:

[email protected]:~$  sh srchfile.sh xxxx /etc

            error: second argument must be a file

            usage: ./srchfile.sh search-pattern file

Add at least 2 more scenarios in your Word document.

Part 2

Description.

Now, write a second Korn Shell script named srch.sh. The srch.sh script will call the srchfile.sh script to perform a specific task and accept 2 command line arguments. The first argument shall be a string (pattern) found in the file being searched. The second command line argument shall be the name of a file or a directory.

Requirements:

The second argument represents either the name of the file to be searched or a directory. If a directory is entered, then all files in the directory shall be searched.

The script srch.sh shall use the script srchfile.sh to search for the string in a given file. If the second argument is a directory, then srch.sh will invoke srchfile.sh repeatedly in a loop.

If the user enters more or fewer than the required number of arguments, the script shall produce an error message and stop.

The script file name must be: srch.sh.

The script permissions must be 705.

Sample Output (provide yours in same Word document)

Sunny Day Scenario, the srch.sh script searching for string root in the file /etc/passwd:

[email protected]:~$  sh srch.sh root /etc/passwd
—— File = /etc/passwd ——

1:root:x:0:0:root:/root:/bin/bash

Rainy Day Scenario, script srch.sh is invoked with only 1 command line argument:

[email protected]:~$  sh srch.sh root

error: must provide 2 arguments

usage: sh srch.sh search-pattern file

Rainy Day Scenario, script srch.sh is invoked with 3 command line arguments:

[email protected]:~$  sh srch.sh root1  root2  root3
error: must provide 2 arguments

usage: sh srch.sh search-pattern file

Add at least 3 more scenarios in your Word document.

d.      In this exercise, you are to write a Korn shell script that spawns 5 processes and then kills them.

Requirements.

This homework assignment requires the creation of 2 Korn shell scripts; 1 script shall be named simple_script.sh and the main script will be named process.sh.

The source code for simple_script.sh is given to you below.

Simple_script.sh script

Create a small shell script file called simple_script.sh with the following contents:
echo “I am simple_script.sh with process ID $$” sleep 5

The simple_script.sh script file name must be: simple_script.sh.