CS 497C – Introduction to UNIXLecture 2: Work with Files and

Directories

Chin-Chih Changchang@cs.twsu.edu

Working with Files and Directories

• Many commands refers to files and directories.

• mkdir – creating a directory$ mkdir docs• ls – listing files and directories$ lsdocs• pwd – show your current directory

Working with Files and Directories

$ pwd/home/romeo• cd – change directory$ cd docs$ pwd/home/remeo/docs• echo – write its arguments to standard

output$ echo This is the first message > note1$ echo This is the second message > note2

Working with Files and Directories

$ lsnote1 note2• cat – concatenate and display files$ cat note1This is the first message.• wc: couting lines, words and characters$ wc note1 1 5 26 notel$ wc –l note1 1 note1

Working with Files and Directories

• ls –l – checking the file attributes

$ ls –l

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• man – find and display reference manual pages

$ man ls

How It All Clicked• Till UNIX came on scene, operating

systems were designed with a particular machine in mind. Programs designed for one system simply wouldn’t run on another.

• Ken Thompson and Dennis Ritchie designed and built a small system having an elegant file system, a command interpreter (the shell) and a set of utilities.

• In 1973, they rewrote the entire system in C.

How It All Clicked

• UC Berkeley created BSD UNIX.• The other brands of UNIX: Xenix, BSDi,

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

• AT&T unify their own System V 3.2, BSD, SunOS and XENIX into System V Release 4 (SVR4).

The Internet• DARPA commissioned UCB to implement

TCP/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 the Internet (and UNIX).

The Windows Threat

• Windows – a graphical user interface (GUI) that uses 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 server market (with Windows NT/2000).

• The MIT introduced X Window – the first windowing system for UNIX.

Standards and POSIX

• In 1992, AT&T’s UNIX business was sold to Novell. Novell then turned over the UNIX to X/OPEN. The Open Group published the single UNIX Specification.

• The Portable Operating System Interface (POSIX) is a set of standard operating interfaces based on UNIX.

• Most UNIX vendors cooperate with The Open Group and also build products based on the UNIX standard.