Unix

When a user logs in to a Unix system, the current working directory normally starts at the directory/file

The time command is used to time a command and not display the actual time. To display the time and date, the date command must be used.

the unix phylosophy is "do a single job correctly" . due to this the authors / creatorscreated unix commands simpler. to do complex tasks the simpler commands are combined. for example

head command is used to displasy the top ten or required number of lines from a file "file"

tail commandis used to displasy the lastten or required number of lines from a file "file"

but if i require to lines from 3rd line to 10th line i does not have the command to do this

i combine head & tail commands

head -10 file | tail -7

by

rami reddy

There are very few similarities beyond some convergent features of their respective user interfaces. Their internal architecture is very different, differing from kernel models to shell integration to executable formats. A comprehensive list of similarities is neither possible nor useful, because it would consist mostly of obvious statements like "They are both operating systems" or "They both have graphical user interfaces, "They both include web browsers" and the like.

Richie and Thompson, along with Kernighan and others.

In computer operating systems, demand paging is an application of virtual memory. In a system that uses demand paging, the operating system copies a disk page into physical memory only if an attempt is made to access it (i.e., if a page fault occurs). It follows that a process begins execution with none of its pages in physical memory, and many page faults will occur until most of a process's working set of pages is located in physical memory. This is an example of lazy loading techniques.

The 'uptime' command will tell you exactly how many users are on the system. There are other variations of this, including counting the number of words from the 'users' command, etc., but this is the easiest.

Usually nothing. The file extension (the .jpeg, .exe, .png, .mov, etc.) tells what kind of file it is. Certain programs deal with certain extensions, like word with .doc, .rtf, and .txt. Paint and photoshop deal with .jpeg, .png, .gif, and .bmp. Powerpoint deals with .ppt, and so on. Hope this helps!

Unix is a classification of operating systems that conform to a certain specification, based on that of the original Unix operating system created by AT&T. Systems certified as Unix can differ drastically, but must meet at least certain common elements.

Solaris is an implementation of Unix created by Sun Microsystems.

Linux is a family of operating systems based on a kernel written by Linus Torvalds. It shares some design goals and similarities with Unix, but has several advanced features and is not completely compatible with Unix. Legally, for a system to be described as "Unix", it must undergo a certification process. No Linux distribution has ever undergone this (very expensive) certification process to make it compliant with Unix standards.

Solaris uses older, POSIX-compliant utilities. Linux typically uses GNU utilities, which are generally compatible, but have different command switches and more features. This is beginning to change with the OpenSolaris project, which incorporates many GNU utilities.

Solaris and Linux both have features that the other lacks, and are not found in other Unix implementations either. These include DTRace and the ZFS file system (in Solaris) and dynamically loadable kernel modules and epoll (in Linux).

Unix was created almost entirely in C. It consists of a main component (called the kernal) and a flotilla of small utilities. Most of these utilities were written in C. Unix distributions usually come with a C compiler so you can create or modify the environment yourself.

However, C is not your only choice. Modern versions of Unix still contain a C compiler, but they often have dozens of other languages available. Most versions of Linux come with a C++ compiler (which is different than C) as well as compilers and interpreters for Java, Perl, and Python. You can generally install hundreds of other languages.

The language you use depends on the type of problem you are solving. Generally you'll use C for basic low-level work, but you'll often pick a higher-level language to solve 'real-world' problems. For example, if you're doing server-side web development, you'll usually use PHP.

AWK is a programming language developed in 1977 by Alfred Aho, Peter Weinberger, and Brian Kernighan. It is was developed as a text-processing language - it has simple syntax to match lines of patterns, separate out the fields, and operate on them.

perl -e 'sub f { my $fu = shift; return 1 if $fu == 1; return f($fu - 1) * $fu; } print f(5), "\n";'

just paste that in to a command prompt, change the print f(5) to print f(6) or whatever you want.

Just like Windows or Apple's mac OS, Linux is an operating system. An operating system is the collection of software that manages the different devices and applications in a computer. For example, some of the software is responsible for shutting down and starting the computer, and some software provides functions such as interacting with devices such as keyboards and mice. Learning to use a Linux system is an excellent opportunity to become familiar with the command line, the most definitive way to communicate with your computer. Plus, as you experiment with different projects, you'll learn about repositories, package management, file permissions, user management, and more.

The full name of CCNA is Cisco Certified Network Associate, and Cisco (Cisco) is the world's largest network equipment company. According to the IT certification examination resource network, CCNA is the primary technical certificate in the Cisco certification system.

First of all, CCNA is a manufacturer's certification, which is internationally accepted. It is an English-only exam that requires a high school English foundation.

Shell scripts are not compiled; they are interpreted (and therefore do not need to be compiled). Just type in the name of the shell script and any parameters it needs to execute.

[ $UID -ne 0] # Checks if the user ID is not 0 (root UID)

# shell script example

if [ -f $1 ]; then

echo $1 is a file

elsif [ -d $1 ]; then

echo $1 is a directory

fi

An old version is just what the name says: an old version, no longer up-to-date. Old versions are typically no longer maintained or supported by the manufacturer, although different industries and manufacturers handle this differently. For example, a washing machine manufacturer will continue supporting an old model for a number of years after its replacement with a more recent model. "Continue supporting" in this context means the retail of spare parts, the supply of repair and diagnostics services, etc. Software products, on the other hand, are often only supported in the current version, plus maybe one version back in the revision history. Exceptions exist with high-value software and foundation software, such as Microsoft's operating systems. Old version products are typically not on sale any more. A trial version is typically only available with software products. Trial versions come at reduced cost, often free, but are typically limited in features or in time. The purpose of a trial version is to allow the future buyer to evaluate the product prior to making a purchase.

The date and time are set in most Unix systems with the 'date' command. The exact syntax can vary, in which case you can find out by using the 'man date' command.

Note: you have to be a root level user to issue this command to change the date or time.

cp -i

mv -i

This is accomplished via two different commands; the sequence would be:

chown bob /etc/yearend

chgrp acctg /etc/yearend

If the perl script outputs to the standard output device, use the I/O redirection operators (>, >>, |) to redirect it somewhere else.

#!/bin/sh

wc -lw "$1"

Several ways to do this. If you just want to see what the files are, you could use:

ls $HOME

ls ~

ls /home/userid, where userid is your logon account