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Unix- Fundamentals of Unix Operating System UNIX is a computer operating system, a control program that works with users to –run programs, –manage resources, and –communicate with other computer systems. • Several people can use a UNIX computer at the same time; hence UNIX is called a multiuser system. Any of these users can also run multiple programs at the same time; hence UNIX is called multitasking. • UNIX is not only the operating system but also a programming language. - Unix is designed by C language

Unix- Fundamentals of Unix Operating System Structure of the UNIX system The UNIX operating system is made up of three parts; the kernel, the shell and the programs. The kernel The kernel of UNIX is the hub of the operating system: it allocates time and memory to programs and handles the file store and communications in response to system calls. The shell The shell acts as an interface between the user and the kernel. When a user logs in, the login program checks the username and password, and then starts another program called the shell. The shell is a command line interpreter (CLI). It interprets the commands the user types in and arranges for them to be carried out. The commands are themselves programs: when they terminate, the shell gives the user another prompt ($ or # on our systems).

Unix- Fundamentals of Unix Operating System

Unix- Fundamentals of Unix Operating System Installing and Updating Cygwin Packages https://www.cygwin.com Cygwin is: a large collection of GNU and Open Source tools which provide functionality similar to a Linux distribution on Windows. a DLL (cygwin1.dll) which provides substantial POSIX API functionality. The Cygwin DLL currently works with all recent, commercially released x86 32 bit and 64 bit versions of Windows, starting with Windows XP SP3.

Unix- Fundamentals of Unix Operating System Flavors of Unix: There are many versions of Unix that are used by lots of people: BSD (from Berkeley) Solaris (Oracle) AIX (IBM) - Advanced Interactive Executive LINUX (free software)

Unix- Fundamentals of Unix Operating System IBM AIX Fundamentals of Unix Operating System The AIX® operating system is designed to deliver outstanding scalability, reliability, and manageability. Best of all, the AIX operating system comes from IBM, the world's leading technology company.

Unix- Fundamentals of Unix Operating System Oracle Solaris

Unix- Fundamentals of Unix Operating System Unix File Structure All the files are grouped together in the directory structure. The file-system is arranged in a hierarchical structure, like an inverted tree. The top of the hierarchy is traditionally called root(written as a slash / )

Unix- Fundamentals of Unix Operating System File Permission

Unix- Fundamentals of Unix Operating System File Permission $ ls -1 pnt -rw-rw---- 1 pntadmin grads 13 Jan 10 23:05 pnt There are three types of permissions: read abbreviated r write abbreviated w execute abbreviated x There are 3 sets of permissions: 1.user 2.group 3.other (the world, everybody else) -rw-rw-r— User Group Others

Unix- Fundamentals of Unix Operating System File Permission The chmod command The chmodcommand changes the permissions of a file or directory $ chmodu+xpnt Here execute permission is provided to user $ chmodg+wpnt Herewrite permission is provided to group $ chmodg-w pnt Here write permission is revoke from group

Unix- Fundamentals of Unix Operating System File Permission Consider permission for each set of users (user, group, other) as a 3-bit # r –4 w –2 x –1 A permission (mode) for all 3 classes is a 3-digit octal # 755 –rwxr-xr-x 644 –rw-r—r-- 700 –rwx------

Unix- Fundamentals of Unix Operating System File Permission $chmod764 pnt Here User has r+w+xpermission ,group has r+wpermission and other has r permission on pntfile $chmod777 pnt Here User has r+w+xpermission ,group has r+w+xpermission and other has r+w+xpermission on pntfile $chmod644 pnt Here User has r+wpermission ,group has r permission and other has r permission on pntfile

Unix- Fundamentals of Unix Operating System shell variables : Variable is a space inside memory .Shell variablesto store information Shell variables are used to affect the behavior of the shell, and many other programs We can access these variables: set new values for some to customize the shell. find out the value of some to help accomplish a task. To assign variable: var1=10 var2=“Hello World” $ echo $var1 $ echo $var2

Unix- Fundamentals of Unix Operating System Shell variables : Some common variables: PATH–list of directories shell searches for non-shell commands PS1–Primary prompt USER–user's login name HOME–user’s home directory PWD–current working directory

Unix- Fundamentals of Unix Operating System Pipes –connecting processes A pipe is a holder for a stream of data. A pipe can be used to hold the output of one program and feed it to the input of another. Separate 2 commands with the “|” character. $ ls -1 | sort $ ls -1 | sort > file1 ls -1 | sort | head > file2

Unix- Fundamentals of Unix Operating System

Unix- Fundamentals of Unix Operating System

Unix- Fundamentals of Unix Operating System

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