Prerequisite: Pipe() and Fork() Basic
Write a C program in which the child process takes an input array and send it to the parent process using pipe() and fork() and then print it in the parent process.
Examples: Suppose we have an array a[]={1, 2, 3, 4, 5} in child process, then output should be 1 2 3 4 5.
Input: 1 2 3 4 5 Output: 1 2 3 4 5
// C program for passing value from // child process to parent process #include <pthread.h> #include <stdio.h> #include <sys/types.h> #include <unistd.h> #include <stdlib.h> #include <sys/wait.h> #define MAX 10 int main()
{ int fd[2], i = 0;
pipe(fd);
pid_t pid = fork();
if (pid > 0) {
wait(NULL);
// closing the standard input
close(0);
// no need to use the write end of pipe here so close it
close(fd[1]);
// duplicating fd[0] with standard input 0
dup(fd[0]);
int arr[MAX];
// n stores the total bytes read successfully
int n = read(fd[0], arr, sizeof (arr));
for ( i = 0;i < n/4; i++)
// printing the array received from child process
printf ( "%d " , arr[i]);
}
else if ( pid == 0 ) {
int arr[] = {1, 2, 3, 4, 5};
// no need to use the read end of pipe here so close it
close(fd[0]);
// closing the standard output
close(1);
// duplicating fd[0] with standard output 1
dup(fd[1]);
write(1, arr, sizeof (arr));
}
else {
perror ( "error\n" ); //fork()
}
} |
Steps for executing above code:
- To compile, write gcc program_name.c
- To run, write ./a.out
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