UNIX Programming

Operating system is a component that on one side manages and controls the hardware and on the other manages the applications.

The mkfs command is used for creating a file system. The exit code returned by mkfs is 0 on success and 1 on failure.

This determines the order in which file systems should be checked.

The sched runs as process 0 on SVR5 system and can be used to set priority for real processes so that they can be given fast access to the kernel.

This command lists the value of the environment variable called VAR_NAME. The $ sign is necessary when a variable's value is being requested.

This is the size field, which refers to the total number of pages in the process.

PID stands for the process identification. This is an unique number that defines the process within the kernel.

This attribute is an User ID number of the user that owns this process.

 A shared memory segment can be allocated, using shmget() system call.

This means the process is waiting to become available.

The fork() system call is the basic way to create a new process.

This system call causes the current process to be split into two processes - a parent and a child.

The eof control character is used to signal the end of input. The letter 'eof' come from end of file. 

The UNIX command 'Man' is a powerful tool that gives complete online access to the UNIX manual.

 The Kill control character allows you to back up over typing mistakes. Whereas, Eraser backs up one character at a time. Kill backs up all the way to the prompt.

Cat command takes any character from standard input , and then echoes them to standard output.

Ordinary files contain text, data or program information.

Directories are containers or folders that hold files and other directories.

The Current directory can be referred to by the . (full stop) character and it refers to your actual location in the file store hierarchy.

Hard link to a file is indistinguishable from the file itself.

UNIX provides each user his own directory known as home directory. Within this, the users can store their own files, and create directories.

Character-oriented device transfers data on a byte-by-byte basis.

This is the process of starting up a computer from a halted or powered-down condition.

The root file system should be present in every UNIX system. It contains the barebones UNIX-the root directory and all the tools and utilities that are just adequate to keep the system booted in single-user mode.

The swapper daemon runs as process 0 on BSD systems. It manages the physical memory by moving the process from physical memory to swap space when more physical memory is needed.