Unix/Linux programming Interview Questions and Answers

1 :: Construct pipes to execute the following jobs?

Who | echo "total users `who|wc -l`"ls | grep -c "poem" | tee filename.txtcat file1 file2 >> filetoappendto.txt??rm -rf dir1 | tee errorlog

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2 :: Explain difference between IPC mechanisms?

Ipc mechanisms are mianly 5 types

1.pipes:it is related data only send from one pipe output is giving to another pipe input

to share resouses pipe are used

drawback:itis only related process only communicated

2.message queues:message queues are un related process are also communicate with message queues

drawback:user dont know which process curently works

share memory:memory shared in distributed systems some memory wants to share some files that time it is use full

semaphores
semaphore is integer type and in semaphore resourses give coding like negetive value means process are wants to use perticular resource waiting only and 0 means no process is waiting and 1 means one resource is free and

sockets:sockets also ipc it is comunicate clients and server

with socket system calls connection oriented and connection less also

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3 :: What type of scheduling is used in Unix?

Multi Level Feedback Queue Scheduling with each queue in round robin.

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4 :: What is stty used for?

Sets options for your terminal.

Print or change terminal characteristics.

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5 :: How would you remove a semaphore / shared memory whose owner processes have died?

ipcrm -sem id ; for semaphores
ipcrm -shm id ; for shared mem

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