CSCI 2467, Fall 2020 Class Activity: graphing and predicting a forking program 1 Forecasting a fork() Consider the program below, which contains a main() function which calls another function called...

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CSCI 2467, Fall 2020 Class Activity: graphing and predicting a forking program 1 Forecasting a fork() Consider the program below, which contains a main() function which calls another function called doit(). The C source for this program is also available in moodle. void do i t ( ) { f o rk ( ) ; p r i n t f ( " h e l l o \n " ) ; return ; } int main ( ) { do i t ( ) ; p r i n t f ( " h e l l o \n " ) ; e x i t ( 0 ) ; } 1.1 Process graph In the space above, draw a process graph, similar to the ones seen in the text and in the lecture slides. Each invocation of doit(), fork(), and printf() should be a node on the graph. 1.2 Output How many lines of output (i.e. how many instances of “hello”) does this program produce? 1 1.3 Change order of main() Test what happens if you modify the original doit.c program to create doit1.c: In main(), if you put the printf() statement before doit(), how does this change the output? Draw a new process graph below and then state how many lines will be printed: ______________ 1.4 Add another fork() to doit() Test what happens if you modify the original doit.c program to create doit2.c: In doit(), if you add a second call to fork() at the beginning of the function, how does this change the output? Draw a new process graph below and then state how many lines will be printed: ______________ 1.5 Replace return with exit(0) in doit() Test what happens if you modify the original doit.c program to create doit3.c: In doit(), if you replace return with exit(0), how does this change the output? Draw a new process graph below and then state how many lines will be printed: ______________ 2 Check your answers Now that you have 3 graphs and 3 answers for the problem above, make a new directory and then create 3 files with the C source for these three examples: doit1.c, doit2.c, doit3.c. After you create each file and make changes to the source code, you can compile each by running make doit1 and so on. (This is simply a shortcut to running the gcc compiler) Run each program and compare to your process graph and prediction. How did the output of those programs compare to what you predicted? 2 Forecasting a fork() Process graph Output Change order of main() Add another fork() to doit() Replace return with exit(0) in doit() Check your answers