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Chmod : It is used for to change permissions on files.
Chown : It is used for to change ownership of a file.
Chgrp : It is used for to change group of the file.

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• touch - to create empty files.(e.g.) - touch ‹filename›
• vi ‹filename›
• cat>filename

Ans: 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.

 Ans: Date

Ans: Two prompts, PS1 (Primary Prompt), PS2 (Secondary Prompt).

Ans:
Cmp - Compares two files byte by byte and displays the first mismatch.
Diff - tells the changes to be made to make the files identical.

Ans: A process group is a collection of one or more processes. Each process group has a unique process ID. A function getpgrp returns the process group id of the calling process.

Ans: When a process calls one of the exec functions that process is completely replaced by the new program. The new program stats execution from main function. The processed does not change across an exec because a new process is not created. But this function replaces the current process with new program from disk.

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• Fully buffered
• Line buffered
• Un buffered

Ans: The bit S_ISVTX is known as sticky bit. If this bit is set for an executable program file, then the first time the program was executed a copy of the programmer’s text was saved in the swap area when the process terminated. The advantage of using this is the program is loaded into memory faster the next time.