You can use shared memory (shm_open(), shm_unlink(), mmap(), etc.). #include <stdio.h> #include <stdlib.h> #include <sys/mman.h> #include <sys/types.h> #include <sys/wait.h> #include <unistd.h> static int *glob_var; int main(void) { glob_var = mmap(NULL, sizeof *glob_var, PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0); *glob_var = 1; if (fork() == 0) { *glob_var = 5; exit(EXIT_SUCCESS); } else { … Read more
I had this snippet in my “special scripts” toolbox, but it got lost (clouds were not common back then), so I was searching for it and came up with this question, surprised to see that it’s missing, I searched more and came back here to post it: <?php ob_end_clean(); header(“Connection: close”); ignore_user_abort(); // optional ob_start(); … Read more
Yes, you are absolutely right. When i teach others GitHub, i would like to explain the concept via an example. Lets take a scenario in which the teacher is conducting an MCQ in his class. He usually make copy of the question paper and distribute it (Forking) to his students so that they can work … Read more
system() calls out to sh to handle your command line, so you can get wildcard expansion, etc. exec() and its friends replace the current process image with a new process image. With system(), your program continues running and you get back some status about the external command you called. With exec(), your process is obliterated. … Read more
The one comes from main() and the other three from every fork(). Notice that all three forks() are going to be executed. You might want to take a look at the ref: RETURN VALUE Upon successful completion, fork() shall return 0 to the child process and shall return the process ID of the child process … Read more
When a child exits, some process must wait on it to get its exit code. That exit code is stored in the process table until this happens. The act of reading that exit code is called “reaping” the child. Between the time a child exits and is reaped, it is called a zombie. (The whole … Read more
This is commonly caused by running out of file descriptors. There is the systems total file descriptor limit, what do you get from the command: sysctl fs.file-nr This returns counts of file descriptors: <in_use> <unused_but_allocated> <maximum> To find out what a users file descriptor limit is run the commands: sudo su – <username> ulimit -Hn … Read more
The main difference between forking and threading approaches is one of operating system architecture. Back in the days when Unix was designed, forking was an easy, simple system that answered the mainframe and server type requirements best, as such it was popularized on the Unix systems. When Microsoft re-architected the NT kernel from scratch, it … Read more
Here’s how to understand it, starting at the for loop. Loop starts in parent, i == 0 Parent fork()s, creating child 1. You now have two processes. Both print i=0. Loop restarts in both processes, now i == 1. Parent and child 1 fork(), creating children 2 and 3. You now have four processes. All … Read more
pid_t child_pid, wpid; int status = 0; //Father code (before child processes start) for (int id=0; id<n; id++) { if ((child_pid = fork()) == 0) { //child code exit(0); } } while ((wpid = wait(&status)) > 0); // this way, the father waits for all the child processes //Father code (After all child processes end) … Read more