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Full Discussion: fork function
Top Forums UNIX for Dummies Questions & Answers fork function Post 46829 by a25khan on Tuesday 27th of January 2004 04:54:45 PM
Old 01-27-2004
Error fork function
hi everyone,
have this little piece of code in order to help you understand my question
Code:
#include<stdio.h>
#include<unistd.h>

int main()
{
	int i, pid;
	pid = fork();

	if(pid<0)
	{
		fprintf(stderr, "fork failed\n");
		_exit(1);
	}
	if(pid==0)
	{
		printf("in Child\n");
		_exit(0);
	}
	printf("in parent\n");
}

/** my question is: according to the definition of fork, it creates an
exact copy of original process. what is the original process here?
is it the whole code i.e. the program where this code is written
i named it as one.c, so is one.c the original process? orrrr
when i do pid = fork(), thats the original process created in one.c?
also does the child process exists only in the if loops if child
succeeds?
about fork() function, how does it generates a number? is it like
generating a random number? i just can't figure out, whats my parent process here and whats my child process here, i m confused with the two.
if fork is created when i do pid = fork(), isn't that the
parent process created? and in order to create a child process
am i not supposed to do pid = fork() again!? and what do the parent and child process share in common and what are their differences. i m aware that fork is done for synchronization but m having trouble with the basic */
appreciate your comments.

code tags added for readability --oombera
Last edited by oombera; 04-12-2004 at 01:18 AM..
 

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LEARN ABOUT OPENSOLARIS

getsid

getsid(2)							   System Calls 							 getsid(2)

NAME

       getsid - get process group ID of session leader

SYNOPSIS

       #include <unistd.h>

       pid_t getsid(pid_t pid);

DESCRIPTION

       The  getsid()  function	obtains the process group ID of the process that is the session leader of the process specified by pid.  If pid is
       (pid_t)0, it specifies the calling process.

RETURN VALUES

       Upon successful completion, getsid() returns the process group ID of the session leader of the specified  process.  Otherwise,  it  returns
       (pid_t)-1 and sets errno to indicate the error.

ERRORS

       The getsid() function will fail if:

       EPERM	The  process  specified  by pid is not in the same session as the calling process, and the implementation does not allow access to
		the process group ID of the session leader of that process from the calling process.

       ESRCH	There is no process with a process ID equal to pid.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       exec(2), fork(2), getpid(2), getpgid(2), setpgid(2), setsid(2), attributes(5), standards(5)

SunOS 5.11							    22 Jan 1996 							 getsid(2)
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