Swapping: Whole process is moved from the swap device to the main memory for execution. Process size must be less than or equal to the available main memory. It is easier to implementation and overhead to the system. Swapping systems does not... Read More

* here is a c code may help u by suraj */ #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <semaphore.h> #include <pthread.h> #include "msecond.h" #include "random_int.h" #define NUM_PHILOSOPHERS... Read More

FIFO are otherwise called as 'named pipes'. FIFO (first-in-first-out) is a special file which is said to be data transient. Once data is read from named pipe, it cannot be read again. Also, data can be read only in the order written. It is... Read More

UNIX is written in C and it is portable. It runs on a range of computers from microprocessors to the largest mainframes. The source code is available and written in high level language which makes it easy to adapt for a particular requirement. Read More

who > file1 Who command lists all the users currently working & output can be stored in a file named file1. Read More

Hard Links : 1. All Links have same inode number. 2.ls -l command shows all the links with the link column(Second) shows No. of links. 3. Links have actual file contents 4.Removing any link ,just reduces the link count , but doesn't affect... Read More

Component Object Model, or COM, is a Microsoft platform for software componentry. It is used to enable cross-application communication and dynamic object creation in any programming language that supports the technology. COM is often used in the... Read More

This is the Kernel process that makes rooms for the incoming pages, by swapping the memory pages that are not the part of the working set of a process. Page-Stealer is created by the Kernel at the system initialization and invokes it throughout the... Read More

The way by which the processes are alloated to CPU to use the CPU time is called scheduling. there are different types of schedulings algorithms 1.FCFS(first come first serve) 2.SJF(shortest job first) 3. SHORTEST JOB NEXT 4.ROUND ROBIN 5.... Read More

new ready running waiting terminate Read More

UNIX Kernel is heart of the operating system. UNIX kernal is loaded first when UNIX system is booted. It handles allocation of devices, cpu, memory from that ponint on. Read More

A semaphore is a type of Interprocess communication resource used for synchronization and mutual exclusion between any two asynchronous processes. Read More

PAGING: Paging memory allocation algorithms divide computer memory into small partitions, and allocates memory using a page as the smallest building block. SEGMENTAION: Segmentation means that a part or parts of the memory will be sealed off from... Read More

It?s the nature of the processes that they refer only to the small subset of the total data space of the process. i.e. the process frequently calls the same subroutines or executes the loop instructions. Read More

The privileged mount system call is used to attach a file system to a directory of another file system; the unmount system call detaches a file system. When you mount another file system on to your directory, you are essentially splicing one... Read More

This command will copy the file abc.txt (picked up from the location $ABC/$SUP/) to the current directory u are working on. The file created on the currect directory will also be of the same name abc.txt Read More

While booting, special process called the 'swapper' or 'scheduler' is created with Process-ID 0. The swapper manages memory allocation for processes and influences CPU allocation. The swapper inturn creates 3 children: the... Read More

Kernel contains 4 data structures for Demand paging. They are, Page table entries, Disk block descriptors, Page frame data table (pfdata), Swap-use table. Read More

ls becomes the input to wc which counts the number of lines it receives as input and instead of displaying this count , the value is stored in file1. Read More

A { wait_for(lock_1) { do something that takes time wait_for(lock_2) { do something } } } B { wait_for(lock_2) { do something that takes time wait_for(lock_1) { do something } } } start A start B A will be holding lock_1,... Read More

cat $str1 $str2 is WRONG - cat command will need file names as input Read More

When you enter 'ls' command to look at the contents of your current working directory, UNIX does a series of things to create an environment for ls and the run it: The shell has UNIX perform a fork. This creates a new process that the... Read More

Protection fault refers to the process accessing the pages, which do not have the access permission. A process also incur the protection fault when it attempts to write a page whose copy on write bit was set during the fork() system call. Read More

When the host is not able to boot , you basically cannot connect to the console. So you can view the messages or any other files. The only alternate is that you can boot ur system with old unix vmunix.old file and see the messages. Let me know if... Read More

The root file system has to be present for the system to execute / bin, /dev, and /etc are always kept on the root system because when the system starts only files in the root system are accessible and some files such as /bin/sh are needed to run at... Read More

Job control in Unix means controlling the execution of jobs. Using fg (foreground), bg(background), jobs, kill, nice etc.. you can actually control the priorities, order and the number of jobs which are being processed. The effective use of these... Read More

The page stealer and the fault handler thrash because of the shortage of the memory. If the sum of the working sets of all processes is greater that the physical memory then the fault handler will usually sleep because it cannot allocate pages for a... Read More

Marshalling is usually required when passing the output parameters of a program written in one language as input to a program written in another language. Read More

When it is started by the shell, a program inherits three open files, with file descriptor 0, 1 and 2 called the standard i/p, the standard o/p, and the standard error. If the program reads ?0? and writes descriptors 1 and 2, it can do I/O without... Read More

All UNIX files have its description stored in a structure called 'inode'. The inode contains info about the file-size, its location, time of last access, time of last modification, permission and so on. Directories are also represented as... Read More

 open(pathname,flag,mode) - open file  creat(pathname,mode) - create file  close(filedes) - close an open file  read(filedes,buffer,bytes) - read data from an open file  write(filedes,buffer,bytes) - write data to an open file ... Read More

Splitting is done by a system call named fork. Proc_id = fork (); splits the program into two copies, both of which continue to run. The only difference between the two is the value returned by fork, the process-id. Two copies of the program are made... Read More

When you execute a program on your UNIX system, the system creates a special environment for that program. This environment contains everything needed for the system to run the program as if no other program were running on the system. Each process... Read More

With the help of kill command we can terminate the process. Syntax: kill pid Kill 0 - kills all processes in your system except the login shell. Read More

Both are same. daemons are the background processes in unix. similarly background processes in windows are called as service agents or service processes. Read More

The kill command takes the PID as one argument; this identifies which process to terminate. The PID of a process can be got using 'ps' command. Read More

Device filles are of 2 types --- charcater device file and block device file type field in the file's inode structure b--- block device file c--- character device file Read More

Process before swapping is residing in the primary memory in its original form. The regions (text, data and stack) may not be occupied fully by the process, there may be few empty slots in any of the regions and while swapping Kernel do not bother... Read More

SQLNET users will show up with a process unique name that begins with oracle, if you do a ps -ef|grep oracle|wc -l you can get a count ofthe number of users. Read More

STUB is A temporary implementaion of part of a program for debugging purposes. LILO (LInux LOader) is a boot loader for Linux. Read More

Unix/ Linux Supports four Prompts PS1, PS2, PS3, PS4 Read More

1. To which operating system is GNU/Linux compatible? a. Windows b. Unix c. it's a system on it's own d. don't know 2. What is the origin of GNU/Linux? a. 1984 by Richard Stallman b. 1987 by Andrew Tannenbaum c. 1991 by... Read More

Question : 1.what is kernel? 2. what is the difference between kernel and microkernel? 3. what is the difference between unix and Linux? 4. what is relational database,hierarchal database. and network database? their difference? ... Read More

#rm -fr <Directory name> Read More

The ?Sticky Bit? is a permission bit that can be set on either a file or a directory. If it is set on a file, then that file will remain in memory after execution, thus ?sticking? in memory. This is useful when running a multi-user program (such as... Read More

syntax indirection : command < filename output re-direction : command > filename Error re-direction : command 2>filename or command Read More

Loading refers to storing large amt of data into the system.linking means one program or page is related to another page or program Read More

FIFO are otherwise called as 'named pipes'. FIFO (first-in-first-out) is a special file which is said to be data transient. Once data is read from named pipe, it cannot be read again. Also, data can be read only in the order written. It is... Read More

The Commond $cat file in unix is used to display the content of the file and where as commond $cat >> file is to append the text to the end of the file without overwritting the information of the file. Incase if the file does not exist in the... Read More

In situations like, where the copy on write bit of a page is set and that page is shared by more than one process, the Kernel allocates new page and copies the content to the new page and the other processes retain their references to the old page.... Read More

After finishing the execution of the fault handler, it sets the modify and protection bits and clears the copy on write bit. It recalculates the process-priority and checks for signals. Read More

When processing a command the searchs for the utility for the command in the directories specified in the PATH varible and it in invokes that utility. That utility will execute the command with help of kernel and the output is given to shell. And... Read More

Shell variables are system environment variables.they include TERM,SHELL, MAIL the output of the shell variable we can see by typing the command $>echo $TERM ansi at the prompt. Read More

Who | echo "total users `who|wc -l`"ls | grep -c "poem" | tee filename.txtcat file1 file2 >> filetoappendto.txt??rm -rf dir1 | tee errorlog Read More

During the fork() system call the Kernel makes a copy of the parent process?s address space and attaches it to the child process. But the vfork() system call do not makes any copy of the parent?s address space, so it is faster than the fork() system... Read More

The set of pages that are referred by the process in the last ?n?, references, where ?n? is called the window of the working set of the process. Read More

The window of the working set of a process is the total number in which the process had referred the set of pages in the working set of the process. Read More

Page fault is referred to the situation when the process addresses a page in the working set of the process but the process fails to locate the page in the working set. And on a page fault the kernel updates the working set by reading the page from... Read More

Valid, Reference, Modify, Copy on write, Age. These bits are the part of the page table entry, which includes physical address of the page and protection bits. Page address Age Copy on write Modify Reference Valid Protection Read More

Kernel in traditional Unix, makes the duplicate copy of the parent?s address space and attaches it to the child?s process, while swapping. Kernel in System V Unix, manipulates the region tables, page table, and pfdata table entries, by incrementing... Read More

A data representation at the machine level, that has initial values when a program starts and tells about how much space the kernel allocates for the un-initialized data. Kernel initializes it to zero at run-time. Read More

The two paging states are: The page is aging and is not yet eligible for swapping, The page is eligible for swapping but not yet eligible for reassignment to other virtual address space. Read More

Page stealer finds the page eligible for swapping and places the page number in the list of pages to be swapped. Kernel copies the page to a swap device when necessary and clears the valid bit in the page table entry, decrements the pfdata reference... Read More

Page fault refers to the situation of not having a page in the main memory when any process references it. There are two types of page fault : Validity fault, Protection fault. Read More

Fault handlers are also an interrupt handler with an exception that the interrupt handlers cannot sleep. Fault handlers sleep in the context of the process that caused the memory fault. The fault refers to the running process and no arbitrary... Read More

If a process referring a page in the main memory whose valid bit is not set, it results in validity fault. The valid bit is not set for those pages: that are outside the virtual address space of a process, that are the part of the virtual address... Read More

These keys have significant meaning sometimes DELETE is called as RUBOUT key. Break is sometimes called INTERRUPT. In most SYSTEMS the delete key stops a program immediately, without waiting for it to finish on some systems, Ctrl-C provides this... Read More

Check your hard disk device and use the fdisk and the harddisk device name eg /dev/sda Read More

If the disk block descriptor does not contain any record of the faulted page, then this causes the attempted memory reference is invalid and the kernel sends a ? Segmentation violation? signal to the offending process. This happens when the... Read More

The kernel reads what you type as you type it, even if it?s busy with something else, so you can type as fast as you want, whenever you want, even when some command is printing at you. Your I/P characters will appear intermixed with the O/P... Read More

On a swap device and not in memory, On the free page list in the main memory, In an executable file, Marked ?demand zero?, Marked ?demand fill?. Read More

Your system may have a command called learn which provides computer aided instruction on the file system and basic commands, the editor, document preparation and even ?C? programming. IF $learn exists on your system, it will teach you what to do from... Read More

It sets the valid bit of the page by clearing the modify bit. It recalculates the process priority. Read More

Cat is the simplest of all the printing commands. Cat prints the contents of all the files named by its arguments. The named file or files are catenated the terminal one after another with nothing between. You have to be quick with CTRL-S to stop... Read More

Grep command searches for files for lines which match a pattern. E.g. g/regular expression/p.grep will also look for lines that don?t match the pattern, when the option-V is sued. grep can be used to search several files in that case it will prefix... Read More

cd ~ This command will direct you to the user directory cd $HOME This command will direct you to the Home directory Read More

The page is first checked for the validity fault, as soon as it is found that the page is invalid (valid bit is clear), the validity fault handler returns immediately, and the process incur the validity page fault. Kernel handles the validity fault... Read More

ZAP, which selectively kills processes, is another program. The main problem with that version is speed; it creates so many processes that it runs slowly, which is especially undesirable for a program that kills errant processes rewriting ZAP in C... Read More

After finishing the execution of the fault handler, it sets the modify and protection bits and clears the copy on write bit. It recalculates the process-priority and checks for signals. Read More

You have to specify the screen size each time you use P. $P-36. Also you could put a shell file in your bin. $cat/usr/you/bin/p Exec/usr/bin/p-36$* $ Another solution is to modify p to use an environment variable that defines the properties of your... Read More

The lowest of I/O is a direct entry into the O.S. your program reads or writes files in chunks of any convenient size. The kernel buffers your data into chunks that match the peripheral devices and schedule operations on the devices to optimize... Read More

The most widely used are: 1. System V (AT&T) 2. AIX (IBM) 3. BSD (Berkeley) 4. Solaris (Sun) 5. Xenix ( A PC version of Unix) Read More

All devices are represented by files called special files that are located in/dev directory. Thus, device files and other files are named and accessed in the same way. A 'regular file' is just an ordinary data file in the disk. A '... Read More

Kernal: It carries out basic operating system functions such as allocating memory, accessing files and handling communications. Shell:A shell provides the user interface to the kernal.There are 3 major shells : C-shell, Bourne shell , Korn shell Read More

One can call to read return 0 which signals the end of file life, if data is written on that file then a subsequent read will be able to find more bytes available. This observation is the basis of a program called readslow which continues to read its... Read More

NTFS-- NTFS is a high-performance and self-healing file system proprietary to Windows XP 2000 NT, which supports file-level security, compression and auditing. It also supports large volumes and powerful storage solution such as RAID. FAT system ... Read More

ex is Unix line editor and vi is the standard Unix screen editor. Read More

Sometimes it is nice to know what specific error occurred; for this purpose all system calls, when appropriate, leave an error number in an external integer called calls, when appropriate, leave an error number in an external integer called errno. By... Read More

A Unix directory is a file containing a correspondence between filenames and inodes. A directory is a special file that the kernel maintains. Only kernel modifies directories, but processes can read directories. The contents of a directory are a... Read More

(1)/bin: contains many programs which will be executed by users (2)/etc : files used by administrator (3)/dev: hardware devices (4)/lib: system libraries (5)/usr: application software (6)/home: home directories for different systems. Read More

The operation of spname is straightforward enough, although there are a lot of boundary conditions to get right. Suppose the file name is /d1/d2/f. The basic ideas is to peel off the first component (/), then search that directory for a name close... Read More

It reads the standard input and sends it to the standard output while redirecting a copy of what it has read to the file specified by the user. Read More

Every file has following attributes:  owner's user ID ( 16 bit integer )  owner's group ID ( 16 bit integer )  File access mode word 'r w x -r w x- r w x' (user permission-group permission-others permission) r-read,... Read More

The input from a pipe can be combined with the input from a file . The trick is to use the special symbol ?-? (a hyphen) for those commands that recognize the hyphen as std input. In the above command the output from who becomes the std input to sort... Read More

The easiest way to store the values of the variables is in a 26-element array; the single-letter variable name can be used to index the array. But if the grammar is to process both variable names and values in the same stack, yacc has to be told that... Read More

A link is a second name (not a file) for a file. Links can be used to assign more than one name to a file, but cannot be used to assign a directory more than one name or link filenames on different computers. Symbolic link 'is' a file that... Read More

The system call mknod creates special files in the following sequence. 1. kernel assigns new inode, 2. sets the file type to indicate that the file is a pipe, directory or special file, 3. If it is a device file, it makes the other entries like... Read More

cmp - Compares two files byte by byte and displays the first mismatch diff - tells the changes to be made to make the files identical Read More

We can connect to Oracle from Unix just by giving the command sqlplus at the prompt and log into Oracle using the appropriate username and password. Read More

grep? is a pattern search command. It searches for the pattern, specified in the command line with appropriate option, in a file(s). Syntax : grep Example : grep 99mx mcafile Read More

Inode has 13 block addresses. The first 10 are direct block addresses of the first 10 data blocks in the file. The 11th address points to a one-level index block. The 12th address points to a two-level (double in-direction) index block. The 13th... Read More

Cat displays file contents. If the file is large the contents scroll off the screen before we view it. So command 'more' is like a pager which displays the contents page by page. Read More

Yes, wc-stands for word count. wc -c for counting number of characters in a file. wc -l for counting lines in a file. Read More

Use ?su? command. The system asks for password and when valid entry is made the user gains super user (admin) privileges. Read More

chmod command is used to change file permissionsyntax : chmod category operation permission filenamewhere category may be u = user ,g = group,o = others,a = alloperation may be '+' = assign permission,'-' = remove permission,'... Read More

A pipe is two or more commands separated by pipe char '|'. That tells the shell to arrange for the output of the preceding command to be passed as input to the following command. Example : ls -l | pr The output for a command ls is the... Read More

A daemon is a process that detaches itself from the terminal and runs, disconnected, in the background, waiting for requests and responding to them. It can also be defined as the background process that does not belong to a terminal session. Many... Read More

There are four possible results from this call: ?kill()? returns 0. This implies that a process exists with the given PID, and the system would allow you to send signals to it. It is system-dependent whether the process could be a zombie. ?kill()?... Read More

Df and du commands are used for checking free space on disk . df -h or df -Humanreadable gives human readable format of free space Read More

$ ls > file1 writes the list of all the files in the folder into a file called file1 $ banner hi-fi > message gives an error coz of the - i guess $ cat par.3 par.4 par.5 >> report writes the contents of the 3 files into a file called... Read More

The ps command prints the process status for some or all of the running processes. The information given are the process identification number (PID),the amount of time that the process has taken to execute so far etc. Read More

Question : What is an advantage of executing a process in background? The most common reason to put a process in the background is to allow you to do something else interactively without waiting for the process to complete. At the end of the... Read More

The system calls used for low-level process creation are execlp() and execvp(). The execlp call overlays the existing program with the new one , runs that and exits. The original program gets back control only when an error occurs. execlp(path... Read More

The term IPC (Inter-Process Communication) describes various ways by which different process running on some operating system communicate between each other. Various schemes available are as follows: Pipes: One-way communication scheme through... Read More

Historic Unix uses Swapping ? entire process is transferred to the main memory from the swap device, whereas the Unix System V uses Demand Paging ? only the part of the process is moved to the main memory. Historic Unix uses one Swap Device and Unix... Read More

 It decides which process should reside in the main memory,  Manages the parts of the virtual address space of a process which is non-core resident,  Monitors the available main memory and periodically write the processes into the swap... Read More

A Map is an Array, which contains the addresses of the free space in the swap device that are allocatable resources, and the number of the resource units available there. This allows First-Fit allocation of contiguous blocks of a resource.... Read More

Kernel follows Round Robin scheme choosing a swap device among the multiple swap devices in Unix System V. Read More

A Region is a continuous area of a process?s address space (such as text, data and stack). The kernel in a ?Region Table? that is local to the process maintains region. Regions are sharable among the process. Read More

When Kernel swaps the process out of the primary memory, it performs the following:  Kernel decrements the Reference Count of each region of the process. If the reference count becomes zero, swaps the region out of the main memory,  Kernel... Read More

/stand directory name vmunix. Read More

Question : How to find some partuicular lines in unix Vi editor which starts with a paricular word and end with another particular word?? For ex - There are 10 lines in the editor and only 4 lines start with the word APPLE and end with the word... Read More

This contains the private data that is manipulated only by the Kernel. This is local to the Process, i.e. each process is allocated a u-area. Read More

All memory space occupied by the process, process?s u-area, and Kernel stack are swapped out, theoretically. Practically, if the process?s u-area contains the Address Translation Tables for the process then Kernel implementations do not swap the u... Read More

fork() is a system call to create a child process. When the parent process calls fork() system call, the child process is created and if there is short of memory then the child process is sent to the read-to-run state in the swap device, and return... Read More

All devices are represented by files called special files that are located in/dev directory. Thus, device files and other files are named and accessed in the same way. A 'regular file' is just an ordinary data file in the disk. A &... Read More

At the time when any process requires more memory than it is currently allocated, the Kernel performs Expansion swap. To do this Kernel reserves enough space in the swap device. Then the address translation mapping is adjusted for the new virtual... Read More

All UNIX files have its description stored in a structure called inode. The inode contains info about the file-size, its location, time of last access, time of last modification, permission and so on. Directories are also represented as files and... Read More

The swapper is the only process that swaps the processes. The Swapper operates only in the Kernel mode and it does not uses System calls instead it uses internal Kernel functions for swapping. It is the archetype of all kernel process. Read More

A Unix directory is a file containing a correspondence between filenames and inodes. A directory is a special file that the kernel maintains. Only kernel modifies directories, but processes can read directories. The contents of adirectory are a list... Read More

 Zombie process: They do not take any up physical memory.  Processes locked in memories that are updating the region of the process.  Kernel swaps only the sleeping processes rather than the ?ready-to-run? processes, as they have the higher... Read More

The swapper works on the highest scheduling priority. Firstly it will look for any sleeping process, if not found then it will look for the ready-to-run process for swapping. But the major requirement for the swapper to work the ready-to-run process... Read More

Every file has following attributes: owner's user ID ( 16 bit integer ) owner's group ID ( 16 bit integer ) File access mode word 'r w x -r w x- r w x' (user permission-group permission-others permission) r-read, w-write, x... Read More

The resident time of the processes in the swap device, the priority of the processes and the amount of time the processes had been swapped out. Read More

A link is a second name (not a file) for a file. Links can be used to assign more than one name to a file, but cannot be used to assign a directory more than one name or link filenames on different computers. Symbolic link 'is' a file that... Read More

 The process?s memory resident time,  Priority of the process and  The nice value. Read More

Nice value is the value that controls {increments or decrements} the priority of the process. This value that is returned by the nice () system call. The equation for using nice value is: Priority = (?recent CPU usage?/constant) + (base- priority) ... Read More

The system call mknod creates special files in the following sequence. 1. kernel assigns new inode, 2. sets the file type to indicate that the file is a pipe, directory or special file, 3. If it is a device file, it makes the other entries like... Read More

 All processes in the main memory are asleep.  All ?ready-to-run? processes are swapped out.  There is no space in the swap device for the new incoming process that are swapped out of the main memory.  There is no space in the main memory... Read More

The privileged mount system call is used to attach a file system to a directory of another file system; the unmount system call detaches a file system. When you mount another file system on to your directory, you are essentially splicing one... Read More

 Memory architecture must based on Pages,  The machine must support the ?restartable? instructions. Read More

Inode has 13 block addresses. The first 10 are direct block addresses of the first 10 data blocks in the file. The 11th address points to a one-level index block. The 12th address points to a two-level (double in-direction) index block. The 13th... Read More

A shell is an interactive user interface to an operating system services that allows an user to enter commands as character strings or through a graphical user interface. The shell converts them to system calls to the OS or forks off a process to... Read More

Unix identifies each process with a unique integer called ProcessID. The process that executes the request for creation of a process is called the 'parent process' whose PID is 'Parent Process ID'. Every process is associated... Read More

The `fork()' used to create a new process from an existing process. The new process is called the child process, and the existing process is called the parent. We can tell which is which by checking the return value from `fork()'. The... Read More

main() { fork(); printf(" Hello World!"); } Answer: Hello World!Hello World! Explanation: The fork creates a child that is a duplicate of the parent process. The child begins from the fork().All the statements after the call to fork() will be... Read More

main() { fork(); fork(); fork(); printf("Hello World!"); } Answer: "Hello World" will be printed 8 times. Explanation: 2^n times where n is the number of calls to fork() Read More

System calls Description fork() To create a new process exec() To execute a new program in a process wait() To wait until a created process completes its execution exit() To exit from a process execution getpid() To get a process identifier of the... Read More

Getting the value of an environment variable is done by using `getenv()'. Setting the value of an environment variable is done by using `putenv()'. Read More

A parent and child can communicate through any of the normal inter-process communication schemes (pipes, sockets, message queues, shared memory), but also have some special ways to communicate that take advantage of their relationship as aparent and... Read More

When a program forks and the child finishes before the parent, the kernel still keeps some of its information about the child in case the parent might need it - for example, the parent may need to check the child's exit status. To be able to get... Read More

At the Kernel Mode. Read More

There are several commands to do this: du, df, or bdf. Read More

cat, more, pg. Read More

command is used to remove a file is rm. Read More

Yes we can remove an open file under UNIX. Read More

It depends on shell, usually a case-esac or an if-endif or fi structure. Read More

Grep is a string search command that parses the specified string from the specified file or files. Read More

An inode is a file status indicator. It is stored in both disk and memory and tracts file status. There is one inode for each file on the system. Read More

Maybe. Some UNIX systems don't clean up well after themselves. Inode problems and dead user processes can accumulate causing possible performance and corruption problems. Most UNIX systems should have a scheduled periodic reboot so file... Read More

Redirection is the process by which input or output to or from a process is redirected to another process. This can be done using the pipe symbol "|", the greater than symbol ">" or the "tee" command. This is one of the strengths of UNIX allowing... Read More

ps -ef|grep zombie or who -d depending on the system. Read More

Using the ps command. Read More

Getting the value of an environment variable is done by using `getenv()'. Setting the value of an environment variable is done by using `putenv()'. Read More

By the use of Use "who am i" comman Read More

Vis that copied its standard input to its standard output, except that it makes all non printing characters visible by printing them as nn, where nnn is the octal value of the character. Vis is invaluable for detecting strange or unwanted characters... Read More

A signal is a message which can be sent to a running process. signals can be initiated by programs, users, or administrators.For example, to the proper method of telling the Internet Daemon (inetd) to re-read its configuration file is to send it a... Read More

As a process executes it changes state according to its circumstances. Unix processes have the following states: Running : The process is either running or it is ready to run . Waiting : The process is waiting for an event or for a resource. ... Read More

The finger command uses data in the passwd file to give information on system users. Read More

When you execute a program on your UNIX system, the system creates a special environment for that program. This environment contains everything needed for the system to run the program as if no other program were running on the system. Each process... Read More

Use the touch command. Read More

Swapping: Whole process is moved from the swap device to the main memory for execution. Process size must be less than or equal to the available main memory. It is easier to implementation and overhead to the system. Swapping systems does not handle... Read More