UNIX-Intro,Terms & Commands

7/30/2019 UNIX-Intro,Terms & Commands

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So,What is the difference between Unix and Linux?Unix is a complete operating system.There are distributors of it like BSD,Solaris

etc

Linux is basically a kernel.OS can be developed using this linux kernel.These allcome under Unix-like systems.we have different distributors likeubuntu,redhat etc

UNIX Introduction:1.Whats so special about UNIX?:supports Multiuser &Multitasking

2.Programs are designed to work together(they are like general tools).3.UNIX systems are usually split, or bundled, into various component

packages. Typical bundling includes the following:

Basic System:Basic commands and utilities.

Programming:Compilers, debuggers, and libraries.

Text Processing:Troff, macros, and related tools.

Networking:Utilities for connecting to remote machines, includingcommands like rlogin, rcp, etc.

Windowing:Graphical user interfaces such as OPEN LOOK and Motif.

4.Anyone Can Program the Unix Shell.


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Salient features of UNIX


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UNIX shellsSeveral different shells are available: you are free to choose the one that best

suits your interests or your application. The most common ones are:

sh

The Bourne shell It is a bit primitive and lacks job controlfeatures (the ability

to move jobs from the foreground to the background). Most UNIX users

consider the Bourne shell superior for shell programming or writing

command files.csh

The C shell It has a lot of nice features that aren't available in the Bourne shell,

including job control and history (the ability to repeat commands that you

have already given). There are a lot of hidden bugs.

ksh

The Korn shell is compatible with the Bourne shell, but has most of the C

shell's features plus some completely new features, like history editing (

the ability to recall old commands and edit them before executing them.) It

is also more reliable than csh


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bash

The "Bourne-again" shell developed by the Free Software Foundation. bash is

fairlysimilar to the Korn shell. It has many of the C shell's features, plus

history editing and a built-in help command.

OVERVIEW OF COMMANDS

Some commands that you type are internal, built into the shell. For example,

the cd command is builtin.That is, the shell interprets that command and

changes your current directory for you. The ls command, on the other hand,

is an external program stored in the file /bin/ls.The shell doesn't start a separate process to run internal commands. External

commands require the shell tofork and exec a new subprocess ; this takes

some time, especially on a busy system.

When you type the name of a command, the shell first checks to see if it is a

built-in command and, if so,executes it. If the command name is anabsolute pathname beginning with/, like /bin/ls, there is no problem: the

command is likewise executed. If the command is neither built-in, nor

specified with an absolute pathname, the shell looks in its search path for

an executable program or script with the given name.


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The search path is exactly what its name implies: a list of directories that the

shell should look through for a command whose name matches what is

typed.The search path isn't built into the shell; it's something you specify in

your shell setup files. The search path is stored in an environment variable

called PATH . A typical PATH setting might look something like this:PATH=/bin:/usr/bin:/usr/bin/X11:/usr/ucb:/home/tim/bin:

UNIX-Intro,Terms & Commands

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