Fork syscall and related issues

MrUser · #1 (**permalink**) 2 Weeks Ago

Hi all,
i just started started learning system programming and want to pursue a career in the sys prog area.
below is the program that use a fork() call.
i read in one of the tutorials that parent process and child process uses different address spaces and runs concurrently.
that meas each process gets some slice of cpu time, then the statements in that process are executed.
my Questions:
1.is there any way to know how much timeslice each process is getting.

2.what kind of scheduling its using

3. can i print the out put one page at a time ( should wait for keypress to print next page)

4. any links that provides good system programming info(message queues, pipes,shared memory etc.. )

5. appications that uses sockets

6. fork returns zero to the child process and some +ve value to parent.
how is it able to return two values.

below is some example prog:

Code:

#include  <stdio.h>
#include  <sys/types.h>
#define   MAX_COUNT  200
void  ChildProcess(pid_t);                /* child process prototype  */
void  ParentProcess(pid_t);               /* parent process prototype */
void  main(void)
{
     pid_t  pid;
     pid = fork();
     if (pid == 0) 
          ChildProcess(pid);
     else 
          ParentProcess(pid);
}
void  ChildProcess(pid_t pid)
{
     int   i;
     char buf[40];
     for(i=1; i <= MAX_COUNT; i++) {
          sprintf(buf, "This line is from pid %d, value = %d\n", pid, i);
          write(1, buf, strlen(buf));
     }
}
void  ParentProcess(pid_t pid)
{
     int   i;    
     char buf[40];
     for(i=1; i <= MAX_COUNT; i++) {
          sprintf(buf, "This line is from pid %d, value = %d\n", pid, i);
          write(1, buf, strlen(buf));
     }
}

pludi · #2 (**permalink**) 2 Weeks Ago

1. No
2. Depends on what scheduler the kernel uses.
3. Yes, but this has nothing to do with system or concurrent programming, but with counting how much output you already produced and waiting after a certain amount.
5. Sendmail, Postfix, Firefox, FTP, SSH, ... pretty much anything using a network.
6. It doesn't. By the time fork() finishes, there are already 2 separate processes. In the parent process it's returning the PID of the child. In the child it returns 0. If it can't spawn a child for any reason, it returns -1 and sets errno.

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