fork system call understanding Post: 302400091

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Homework and Emergencies Homework & Coursework Questions fork system call understanding Post 302400091 by MrUser on Tuesday 2nd of March 2010 07:19:11 AM

03-02-2010

Registered User

fork system call understanding

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1. The problem statement, all variables and given/known data:

i have a problem in understanding the behaviour of fork .

i understood fork as to create a new process and all the statements that fall after fork are executed by both old and new process.

here's the code i have written and i dont understand how its produced so - called out put.

2. Relevant commands, code, scripts, algorithms:

3. The attempts at a solution (include all code and scripts):

Code:

#include<stdio.h>

int main( void ) {
        int i ;
        i = 0 ;
        int x;
        while ( i < 2) {
                printf("before fork():getpid()= %d \n", getpid());
                x = fork();
                if ( x == 0 ) {
                        printf("in child when i = %d ", i);
                        printf("getpid()= %d", getpid());
                        printf("getppid()= %d\n",getppid());
                }
                else {
                        printf("in parent when i = %d ", i);
                        printf("getpid()= %d", getpid());
                        printf("getppid()= %d\n",getppid());
                }
                i++;
                printf("\n");
        }
return 0;
}

the out put what i am getting is :

Quote:

before fork():getpid()= 6864
in parent when i = 0 getpid()= 6864getppid()= 1777

before fork():getpid()= 6864
in child when i = 0 getpid()= 6865getppid()= 6864

before fork():getpid()= 6865
in child when i = 1 getpid()= 6866getppid()= 6864

in child when i = 1 getpid()= 6867getppid()= 6865

in parent when i = 1 getpid()= 6864getppid()= 1777

in parent when i = 1 getpid()= 6865getppid()= 6864

please just provide the meaning full description or modify the code so that i can understand it easily.

4. Complete Name of School (University), City (State), Country, Name of Professor, and Course Number (Link to Course):

VSU,Bangalore,India,Govardhan.

Note: Without school/professor/course information, you will be banned if you post here! You must complete the entire template (not just parts of it).

MrUser

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LEARN ABOUT OPENSOLARIS

getpid

getpid(2)							   System Calls 							 getpid(2)

NAME

       getpid, getpgrp, getppid, getpgid - get process, process group, and parent process IDs

SYNOPSIS

       #include <unistd.h>

       pid_t getpid(void);

       pid_t getpgrp(void);

       pid_t getppid(void);

       pid_t getpgid(pid_t pid);

DESCRIPTION

       The getpid() function returns the process ID of the calling process.

       The getpgrp() function returns the process group ID of the calling process.

       The getppid() function returns the parent process ID of the calling process.

       The getpgid() function returns the process group ID of the process whose process ID is equal to pid, or the process group ID of the calling
       process, if pid is equal to 0.

RETURN VALUES

       The getpid(), getpgrp(), and getppid() functions are always successful and no return value is reserved to indicate an error.

       Upon successful completion, getpgid() returns the process group ID. Otherwise, getpgid() returns (pid_t)-1 and sets errno to  indicate  the
       error.

ERRORS

       The getpgid() function will fail if:

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

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

       The getpgid() function may fail if:

       EINVAL	 The value of the pid argument is invalid.

ATTRIBUTES

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

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Committed 		   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Async-Signal-Safe 	   |
       +-----------------------------+-----------------------------+
       |Standard		     |See standards(5). 	   |
       +-----------------------------+-----------------------------+

SEE ALSO

       Intro(2), exec(2), fork(2), getsid(2), setpgid(2), setpgrp(2), setsid(2), signal(3C), attributes(5), standards(5)

SunOS 5.11							    27 Jan 2009 							 getpid(2)

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