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11. What Are The Differences Among A System Call, A Library Function, And A UNIX Command?
Date Posted: 07/02/2012
Ans: A system call is part of the programming for the kernel. A library function is a program that is not part of the kernel but which is available to users of the system. UNIX commands, however, are stand-alone programs; they may incorporate both system calls and library functions in their programming.
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12. Briefly Describe The Shell’s Responsibilities?
Date Posted: 07/02/2012
Ans:
- Program execution
- variable and file name substitution
- I/O redirection
- pipeline hookup
- environment control
- interpreted programming language
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13. What Is The Chief Difference Between The –v And –x Option S To Set?
Date Posted: 07/02/2012
Ans: The –v option echoes each command before arguments and variables have been substituted for; the –x option echoes the commands after substitution has taken place.
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14. Is There A Way To Erase All Files In The Current Directory, Including All Its Sub-directories, Using Only One Command?
Date Posted: 07/02/2012
Ans: Yes, that is possible. Use “rm –r *” for this purpose. The rm command is for deleting files. The –r option will erase directories and subdirectories, including files within. The asterisk represents all entries.
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15. What Is A Typical Syntax Being Followed When Issuing Commands In Shell?
Date Posted: 07/02/2012
Ans: Typical command syntax under the UNIX shell follows the format:
Command [-argument] [-argument] [--argument] [file]
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16. What Scheme Does The Kernel In Unix System V Follow While Choosing A Swap Device Among The Multiple Swap Devices?
Date Posted: 07/02/2012
Ans: Kernel follows Round Robin scheme choosing a swap device among the multiple swap devices in Unix System V.
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17. What Are The Criteria For Choosing A Process For Swapping Out Of The Memory To The Swap Device?
Date Posted: 07/02/2012
Ans: The process’s memory resident time, Priority of the process and the nice value.
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18. What Are The Criteria For Choosing A Process For Swapping Into Memory From The Swap Device?
Date Posted: 07/02/2012
Ans: The resident time of the processes in the swap device, the priority of the processes and the amount of time the processes had been swapped out.
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19. Is The Process Before And After The Swap Are The Same? Give Reason.
Date Posted: 07/02/2012
Ans: Process before swapping is residing in the primary memory in its original form. The regions (text, data and stack) may not be occupied fully by the process, there may be few empty slots in any of the regions and while swapping Kernel do not bother about the empty slots while swapping the process out. After swapping the process resides in the swap (secondary memory) device. The regions swapped out will be present but only the occupied region slots but not the empty slots that were present before assigning. While swapping the process once again into the main memory, the Kernel referring to the Process Memory Map, it assigns the main memory accordingly taking care of the empty slots in the regions.
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20. How Is The Command “$cat File2 “different From “$cat >file2 And >> Redirection Operators?
Date Posted: 07/02/2012
Ans: is the output redirection operator when used it overwrites while >> operator appends into the file.
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