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Lecture 2: Work with Files and

Directories

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Working with Files and

Directories Many commands refers to files and

directories.

mkdircreating a directory$ mkdir docs

lslisting files and directories

$ lsdocs

pwdshow your current directory

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Working with Files and

Directories$ pwd/home/romeo

cdchange directory

$ cd docs$ pwd

/home/remeo/docs

echowrite its arguments to standardoutput

$ echo This is the first message > note1

$ echo This is the second message > note2

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Working with Files and

Directories$ lsnote1 note2

catconcatenate and display files

$ cat note1This is the first message.

wc: couting lines, words and characters

$ wc note11 5 26 notel

$ wcl note1

1 note1

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Working with Files and

Directories lslchecking the file attributes

$ lsl

total 2-rw-r--r-- 1 romeo staff 26 Aug 22 02:05 note1

-rw-r--r-- 1 romeo staff 27 Aug 22 02:06 note2

manfind and display reference manual pages$ man ls

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How It All Clicked

Till UNIX came on scene, operatingsystems were designed with a particularmachine in mind. Programs designed forone system simply wouldnt run on another.

Ken Thompson and Dennis Ritchiedesigned and built a small system having anelegant file system, a command interpreter

(the shell) and a set of utilities. In 1973, they rewrote the entire system in

C.

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How It All Clicked

UC Berkeley createdBSD UNIX.

The other brands of UNIX: Xenix, BSDi,

BSD/OS, FreeBSD, SunOS, Solaris, HP-UX, AIX, Ultrix, Digital UNIX, IRIX, SCOOpen Server, SCO UnixWare.

AT&T unify their own System V 3.2, BSD,

SunOS and XENIX into System V Release 4(SVR4).

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The Internet

DARPA commissioned UCB to implementTCP/IP on BSD UNIX.

TCP/IP is a set of protocols used by the

Internet for communication. The incorporation of TCP/IP into UNIX and

its use as the basis of development were two

key factors in the rapid growth of theInternet (and UNIX).

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The Windows Threat

Windowsa graphical user interface(GUI) thatuses the mouse rather than

arcane and complex command options

to execute a job. Windows first swept the desktop market

(with Windows 3.1/95/98/Me) and then

made significant inroads into the servermarket (with Windows NT/2000).

The MIT introduced X Windowthe

first windowing system for UNIX.

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Standards and POSIX

In 1992, AT&Ts UNIX business was soldto Novell. Novell then turned over theUNIX to X/OPEN. The Open Group

published the single UNIX Specification. The Portable Operating System Interface

(POSIX)is a set of standard operatinginterfaces based on UNIX.

Most UNIX vendors cooperate with TheOpen Group and also build products basedon the UNIX standard.