What does the command “ $who | sort –logfile > newfile” do?

Unix Interview Questions

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79. What does the command “ $who | sort –logfile > newfile” do?

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 logfile, 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 newfile.

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Other Interview Questions

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• How can a parent and child process communicate?
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• What Happens when you execute a program?
• What Happens when you execute a command?
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• What is the main goal of the Memory Management?
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• What are the entities that are swapped out of the main memory while swapping the process out of the main memory?
• What is Fork swap?
• What is Expansion swap?
• How the Swapper works?
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• What are the requirements for a swapper to work?
• What are the criteria for choosing a process for swapping into memory from the swap device?
• What are the criteria for choosing a process for swapping out of the memory to the swap device?
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• What are conditions on which deadlock can occur while swapping the processes?
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• What is the window of the working set of a process?
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• What are the bits that support the demand paging?
• How the Kernel handles the fork() system call in traditional Unix and in the System V Unix, while swapping?
• Difference between the fork() and vfork() system call?
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• What are the phases of swapping a page from the memory?
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• In what way the Fault Handlers and the Interrupt handlers are different?
• What is validity fault?
• What does the swapping system do if it identifies the illegal page for swapping?
• What are states that the page can be in, after causing a page fault?
• In what way the validity fault handler concludes?
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• 74. What is ex and vi ?
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