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+Return to [[os:|Operationg Systems home]]
+----
+====== Operating Systems Course: Lab10 ======
+===== Laboratory number 10 (pseudo-exam test) =====
+==== Exercise 01 ====
+Implements with the semaphore primitives the prologue and the epilogue of 4 functions A, B, C, and D, so that the processes that call them respect the following //path expression//:
+<code txt>
+path ( A+B; {C}; D ) end
+</code>
+The meaning of this path expression is that the set of processes can:
+  * call function A **or** function B in //mutual exclusion// (i.e., a process waits if the function is used by another process)
+  * then, it can call function C (that can be executed concurrently by all the processes)
+  * finally, it can call function D.
+If, for instance, the first of all the functions called is function D, the process that called it, it is blocked until other processes have called A or B, and then C.
+The //path expression// is cyclic, i.e., when function D is executed, functions A or B (etc.) can be performed again, without waiting.
+**Suggestion**\\
+Refer to the solution of Readers & Writers.
+==== Exercise 02 ====
+Illustrate the characteristics, differences and typical use of the system calls ''fork'', ''execve'', and ''system''.
+==== Exercise 03 ====
+Realize a bash script that receives two parameters:
+  * the name of a user of the system
+  * the name of a directory.
+The script must recognize all the files of the specified user that are in the directory and its subdirectories, and that contain (at least) a row that begins with the string "***Da modificare".
+In those files you need to:
+  * delete this row
+  * append to the name of the file the string "''_mod''".
+Check the correct passage of the parameters.
+==== Exercise 04 ====
+Write a multi-thread program that sorts a vector of integer numbers using the algorithm merge-sort and using concurrency instead of recursion.
+Each thread, starting from the initial one must:
+  * receive a vector to sort of dimension ''n''
+  * subdivide the vector in two parts of dimension ''n/2''
+  * activate a thread on each part of the vector
+  * wait for the termination of both threads
+  * merge the two received parts of dimension ''n/2'' and already sorted, by performing a merge, and generating a single sorted vector of dimension ''n''.
+Note that the termination condition occurs when a thread receives a vector of dimension ''n=1''.
+The vector and its dimension can be read from the keyboard, from a file, or generated randomly.
+==== Exercise 05 ====
+Given the following processes, with the relative arrival times and their duration:
+<code txt>
+P1 0 11
+P2 2  9
+P3 4  7
+P4 6  5
+P5 8  3
+</code>
+Report the Gantt charts and calculate the average waiting times for the algorithms FCFS, SJF and SRTF.
+==== Exercise 06 ====
+With reference to deadlock prevention through the hierarchical use of resources, describe the technique and demonstrate that it cannot lead to deadlock.

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