Systems Programming
Purpose: Understand the fork() regarding its returning values, global/local variables declared in the parent's process, and processing
Instruction:
Attached is a lab.c file containing a fork() statement. Compile and run it. Explain the output of this program.
Thing to submit:
Submit a word file to explain the following questions:
Thing to submit:
Provide your answer in a Word document.
//this is the lab9.c file
#include <unistd.h> #include <sys/types.h> #include <errno.h> #include <stdio.h> #include <sys/wait.h> #include <stdlib.h> int var_global = 0; /* A global variable*/ int main(void) { pid_t forkRet; int var_local = 0; forkRet = fork(); if(forkRet >= 0) // fork was successful { if(forkRet == 0) // child process { var_local++; var_global++; printf("\n Child Process :: var_local = %d, var_global = %d my PID = %d\n", var_local, var_global, getpid()); } else //Parent process { var_local = 10; var_global = 20; printf("\n Parent process :: var_local = %d, var_global = %d\n my PID = %d", var_local, var_global, getpid()); } } else // fork failed { printf("\n Fork failed, quitting!!!!!!\n"); return 1; } return 0; }
fork call creates an identical process having the same local and global variable values before fork and then both process run next instructions of the parent process.
1. When fork is called, parent will get child's process id and child will get process id as zero.
2. After the execution of fork, one more process which is identical is created. This identical process is child process which has PID as zero.
3. After fork call, OS can give control to any process. If it is child process(PID=0) then child process having everything same before fork call in parent process is executed. Else it parent process continues. Initially, the values are the same, but to identify which process OS ran, we give them different value. Here if control goes to child process then it will print give var_local and var_global values as 1. If parent gets control then var_local=10 and var_global=20
Systems Programming Purpose: Understand the fork() regarding its returning values, global/local variables declared in the parent's...
Explain what the problem is within the program. Fix the problem when you create a child process per column. The code is given below. So basically, after the child processes have successfully excuted their code, the final print statement does not give the correct values. It prints the original matrix rather than the multiplied matrix.#include #include #include #include int main(int argc, char *argv[]){ int row = 0; int column = 0; row = atoi(argv[1]); column = atoi(argv[2]); int *A = ...
Source code to modify:
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
int main()
{
pid_t pid;
/*fork a child process*/
pid = fork();
if (pid<0){ /*error occured*/
fprintf(stderr,"Fork failed\n");
return 1;
}
else if (pid == 0) { /*child process */
printf("I am the child %d\n",pid);
execlp("/bin/ls","ls",NULL);
}
else { /*parent process */
/*parent will wait for the child to complete*/
printf("I am the parent %d\n",pid);
wait(NULL);
printf("Child Complete\n");
}
return 0;
}
1. Write program codes for 3.21 a and...
Q1) Including the initial parent process, how many processes are created by the program shown in Figure 1? Give an explanation for your answer. You can include an output statement to test and run the program. A sample output statement could be: printf("Testing......"); #include <stdio.h> #include <unistd.h> int main() { /*fork a child process*/ fork(); /*fork another child process*/ fork(); /*fork another child process*/ fork(); return 0; } Figure 1a - How many processes are created? Another version, now displaying...
Question 3: [2+2]a) What, to whom and how many values a fork system call returns? b) Assuming there is no syntax error, what is the output for the following C program for linux? All of you may need to put screenshot of your PC in which Terminal login must be your arid number.int main(){ pid_t fork_return; fork_return = fork(); if (fork_return == 0) { execlp("/bin/ls", "ls", NULL); printf("Child process ID: %d\n", getpid()); exit(0); } else { wait (NULL); printf("Parent process ID: %d\n", getpid()); } return 0;}
Directions: use only the signal mechanism system calls don’t use ( wait() or pipe() )in this problem. You can still read/write from/to a file. You must use ( kill() and pause() ) system calls. rewrite code below to do kill and pause system calls #include <fcntl.h> #include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/wait.h> // Function ptototypes int readX(); void writeX(int); int main() { int pid; // pid: used to keep track of the child process int x...
Arid No is 19-arid-898Question 3: [2+2]a) What, to whom and how many values a fork system call returns? b) Assuming there is no syntax error, what is the output for the following C program for linux? All of you may need to put screenshot of your PC in which Terminal login must be your arid number.int main(){ pid_t fork_return; fork_return = fork(); if (fork_return == 0) { execlp("/bin/ls", "ls", NULL); printf("Child process ID: %d\n", getpid()); exit(0); } else { wait (NULL); printf("Parent process ID: %d\n",...
Figure 〈 1013 > int main pid t pidfork if (pid0) printt "In child process: x*d\n",-x) exit (0) printf ("In parent process: x return 0 *d\n", ++x) Part A- The Output of fork Let's examine the behavior of fork0 through a simple example. Consider the program in Figure 1. Figure 1) This program will produce two lines of output when executed. What are the values of x in each of these lines? Separate your answers for the first and second...
#include <sys/types.h> #include <stdio.h> #include <unistd.h> int value = 10; int main() { pid_t pid; pid = fork(); if (pid == 0) { value = value + 100; } else if (pid > 0) { value = value -100; printf("PARENT: value= %d \n", value); //Line A wait (NULL); } } (i) What will be the output in Line A? Justify your answer. (ii) Do you think there is synchronization problem in updating the variable value? Justify your answer.
Problem la Points (20) Draw the process tree for the program shown below. #include<sys/types.h> #include<stdio.h> #include<unistd.h> int value = 5; int main() pid_t pid; pid = forko; if(pid ==0) { */ Child Process */ forkO; value += 15; return 0; else if (pid > 0) {/* Parent process */ forkO; forkO; wait(NULL); printf("Parent: value = %d", value); /* LINE A */ return 0;