Ans: ls become 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.

Ans: 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 , meanwhile sort opens the file log file, the contents of this file is sorted together with the output of who (rep by the hyphen) and the sorted output is redirected to the file new file.

Ans: Yes, wc-stands for word count.
WC -c for counting number of characters in a file.
WC -l for counting lines in a file.

Ans:  Yes, it stands for ‘disk usage’. With the help of this command you can find the disk capacity and free space of the disk.

Ans: $ echo *
It is similar to ‘ls command and displays all the files in the current directory.

Ans: $od -cbd file_name c – character, b – binary (octal), d-decimal, od=Octal Dump

Ans: rm -r *

Ans: Kill $!

Ans: Choosing a swap device among the multiple swap devices?
Kernel follows Round Robin scheme choosing a swap device among the multiple swap devices in Unix System V.

Ans: 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.