Question

In Linux:
- Please describe ( Shell Command-Line Expansion) and provide an example.
- Please describe the meaning of ( running a process in the background ) with your example.
- Please describe how you can use ( noclobber ) with example.

Answer 1

Answer :

1) In Linux, Shell commands are the instructions given to the processor which returns results in the form of some output.

• Line expansion is nothing but solving the commands added on command line in the correct order.
• There are various types of Shell Command :

1. ECHO : This is the basic command which prints the output to the screen

2.LS : List out the file available in server or that particular directory.

3. Bracket Expression : Bracket can be used to show sequential output like numbers or alphabets.

4. Tilde Expression : By using tilde operator one can see the particular output defined in linux like date , time, username.

2) Running Process in Background :

• In linux processes can be run in background. If there is multicore processor then processes can be run on different cores.
• Multiple processes can be run simultaneously,this is called multiprocessing.
• One can start process in background by simply typing BG on command line.
• '&' sign is also used to run process in background mode.

3) NoClobber :

• NoClobber is nothing but preventing the overwrite operation by accidentally on already existing file.
• We can set noClobber by using following Command.

LS > LIST

set -o noclobber

LS > LIST

If you want to overwrite already existing file, then set +O noclobber .

No error message is given in below example.

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