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Unix
Unix is a family of operating systems primarily designed for servers, mainframes, and high-end workstations. First created in 1969, Unix systems are renowned for their security and stability.
1,127 Questions
Is compiler a part of operating system?
compiler basically translator of one language to desired languages...ex-c language to m/c redable format and os is a system software which provides interfaces between applicaton programs and hardware....so os is a interface unit system software and compiler just a translator....
Why is the Unix operating system virus free?
First of all, Unix (and even Linux) is NOT virus free. Although rare, there are viruses for such systems.
One of the primary reasons that Unix / Linux do not get as many viruses is that the ability of different users is limited. Non-technical users will be restricted in their ability to install, run, or modify software. More experienced users will usually be given more privileges. Without inexperienced users installing software at a whim, over 90 % of the threat of viruses and malware is removed.
Linux is even further protected against viruses because Linux is by nature a heterogeneous platform. To be effective, the program would have to be capable of affecting multiple versions of the kernel, and use exploits in a variety of programs.
What does the command kill -9 do in Unix?
Kill is a program that can terminate or send a signal to process.
kill -9 pid
Would send signal 9 to process having specific pid. 9 Means KILL signal that is not catchable or ignorable. In other words it would signal process (some running application) to quit immediately.
pid - process identifier.
How do you find your IP address from a UNIX command line?
Steps to be followed for finding your computer's ip address in Windows XP:
1.Start->Run->cmd prompt
2.In that,just type ipconfig and then click enter
For example: It will show ip address like 74.110.208.65 .
You can also find your IP address by using Ip-details.com .
What is unix schedular and how it work?
There are two standard job schedulers in Unix - 'at' and 'cron'. Neither can be answered in a short answer so it is suggested that you do an internet search on either of these two commands, or use the 'man' or 'info' command on 'at' or 'cron' on your Unix/Linux system.
What are the advantages of unix os over ms-dos os?
Yes and no. If you have the hardware resources to run UNIX/Linux then you should. DOSBox can run any DOS program in UNIX, so there is no need for DOS if you can run UNIX. However, if you have an older computer or an embedded system where UNIX or Linux would have too much overhead, DOS is a better choice.
What are the charateristics of UNIX operating system?
The UNIX Operating System is available on machines with a wide range of computing power, from microcomputers to mainframes, and on different manufacture's machines. No other operating system can make this claim. We see the reasons of popularity and success of UNIX.
The reasons are
Portability:
The system is written in high-level language making it easier to read, understand, change and, therefore move to other machines. The code can be changed and complied on a new machine. Customers can then choose from a wide variety of hardware vendors without being locked in with a particular vendor.
Machine-independence:
The System hides the machine architecture from the user, making it easier to write applications that can run on micros, mins and mainframes.
Multi-User Operations:
UNIX is a multi-user system designed to support a group of users simultaneously. The system allows for the sharing of processing power and peripheral resources, white at the same time providing excellent security features.
Hierarchical File System:
UNIX uses a hierarchile file structure to store information. This structure has the maximum flexibility in grouping information in a way that reflects its natural state. It allows for easy maintenance and efficient implementation.
UNIX shell:
UNIX has a simple user interface called the shell that has the power to provide the services that the user wants. It protects the user from having to know the intricate hardware details.
Pipes and Filters:
UNIX has facilities called Pipes and Filters which permit the user to create complex programs from simple programs.
Utilities:
UNIX has over 200 utility programs for various functions. New utilities can be built effortlessly by combining existing utilities.
Software Development Tools:
UNIX offers an excellent variety of tools for software development for all phases, from program editing to maintenance of software,
Data structures that contain information about files in Unix file systems that are created when a file system is created. Each file has an inode and is identified by an inode number (i-number) in the file system where it resides. inodes provide important information on files such as user and group ownership, access mode (read, write, execute permissions) and type
How many different kill signals can a kill command signal send to a certain process?
This varies depending on which system you are speaking about. The easiest way to find the signals are to issue a "kill -l" command (that is a small el, not a digit 1).
Why unix is a multiprogramming os?
Those are two separate and totally unrelated concepts.
Linux and Unix are considered multi-user systems because they support separate user accounts with different levels of access privilege. A single-user system may have more than one "account", but there is no administrative difference between them.
Linux and most modern versions of Unix are multiprocessing operating systems because they support more than one processor in a system and can allocate processes to different processors.
How does vi editor work in unix?
The Linux 'vi editor' is an editor that is text based. It can be used like notepad in Windows based systems. It can also be used for editing configuration files.
Different types of file in unix?
Regular file
Text or binary data
Directory
Contains other files and directories.
Executable file
File with the "execute permission" set
Symbolic link
File is a "shortcut" that points to another file.
Device special file
An interface to a piece of hardware, such as a printer.(In UNIX devices are treated as "files")
Named pipe
An interface to a network program.
"Best" is often a matter of opinion, and can be highly subjective. Mac OS X, Solaris 10, AIX,and z/OS are the only major certified Unix operating systems still under development. Mac OS X is the most popular Unix desktop, and Solaris 10 is the most popular one on large servers.
What is the command to run a unix program?
Just type the name of the program. If you want to run the dump program, type dump. if you want to open the links web browser, type links. .....
Some programs take arguments, for example the cat program accepts one or more files as an argument, so you could call it by typing
$ cat file1 [file2, file3...]
Explain out put of the ls-l command?
If you mean the ls command in linux/unix, it is the command to list the contents of a directory. A 'ls -l' will display the complete information including the permissions, owners, size and when last modified in date and time.
e.g.
root\usr\sample $ ls -l
drwxr-xr-x 1 root root 4096 Nov 26 2007 sample.txt
root\usr\sample $ ll
drwxr-xr-x 1 root root 4096 Nov 26 2007 sample.txt
root\usr\sample $ ls
sample.txt
The output of the ls -l and ll command is in the following format. First of the 10 characters shows the type of the item (directory/file/link etc) and the remaining shows the permissions of root, user and group. Next is the number of directories, next is group to which the item belongs, next size of the dirctory/file, next the date on which the directory/file was last modified and the directory/file name.
In unix what does the wc command output?
wc is used to count the characters/words/lines in a file or files. You might use it to see how productive you've been (did you finish that 5000 word essay you were supposed to write) or to see how productive some one else has been...
The options control characters/words/lines: with no options it gives all three:
$ wc notes
56 219 1607 notes
There are 56 lines, 219 words, 1607 characters.
$ wc -l notes
56 notes
I just wanted to know how many lines.
It won't find it.
What is difference between block special file and character special file?
A block special file that provides access to a device that transfers in groups of a fixed size. For example, a disk.
A character special file that provides access to a device that transfers in increments of a single character; for example, a terminal.
What are shell variables Give example?
A shell variable is a temporary location in memory that can be used to store and retrieve information.
For example, the following creates a shell variable and then prints it out:
stuff="Hi there"
echo $stuff
will echo out 'Hi There' to the screen. It has the words "Hi There" saved in a memory location called $stuff, which can be retrieved by its name.
Grep is a command line application that is used to search a file or files and extract data from it/them according to a pattern or filter if you prefer. Grep stands for global regular-expression. There are many versions of grep available and regular expressions (for pattern matching) are available in most modern scripting languages such as ruby, python, perl, php, vb, etc. Grep, ngrep, egrep, etc. are available for multiple platforms including windows. They are well documented and can be downloaded for free.
What command to change directory?
CD
Example:
CD <sub-directory>
Use
CD ..
to go up a directory.
You can also enter a full path to go straight to that directory. Eg:
CD windows/system/etc
What is the difference between soft links and hard links in UNIX?
Consider this example:
$ date > foo
$ rm foo
Typically, you create a file, and it has a ref-count of 1 for its entire lifetime, and eventually we delete the directory entry, decrement the ref-count, and reclaim the inode and data blocks.
Now consider this example:
$ date > foo1
$ ln foo1 foo2
$ rm foo1
$ cat foo2
In this case, the 1st name disappears, but the original data are still available via the 2nd name. This will continue to be true even if we add and delete many names, and even if we move those names up and down the directory hierarchy within the same filesystem, as long as at least one reference remains. Deleting that last name will reclaim the inode and data blocks, too. If you are familiar with RDBMs, you might think of it in terms of referential integrity.
Soft links, on the other hand, have very little to do with all that. Here are two commands which bear some similarity to each other:
$ echo 'Go look at foo2' > bar
$ ln -s foo2 baz
The first offers human-readable instructions, while the second phrases those instructions in terms the filesystem understands. In both cases, if someone rm's foo2 we won't know about it until we "cat baz" or consult bar and notice that foo2 has been pulled out from under us. Symlinks are simple. There is no ref-counting and no guarantees of integrity when it comes to symlinks. That said, they are still enormously useful. Note that symlinks can cross filesystems, a feat which hard links were not designed to handle.
