forking. sharing global data in childs Post: 302264007

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Top Forums Programming forking. sharing global data in childs Post 302264007 by anup13 on Wednesday 3rd of December 2008 01:58:27 AM

12-03-2008

Registered User

forking. sharing global data in childs

hi, i want to write a code for forking 3 4 child. n wants that every child process one of the account from global account list. i wrote a program for that, but problem is every child is processing every account in list. what can me done to avoid it.
attaching code with it

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <sys/types.h>
#include <sys/wait.h>

#define nProcess 2

struct timeval tp1;
struct timeval tp2;

long proc_id_A[5];
char filename[100];

static unsigned int trx_nr=0;
int *prt=&trx_nr;

struct record_log
{
   int account_id;
};
typedef struct record_log record_log;
static record_log records[] = {85013,86709,86712,84966,84955};

static record_log *trx;

void get_transaction()
{
	trx=&records[*prt];
	(*prt)++;
}

void start_processing();

main()
{
 	int i,i_pid,i_no_of_process=0,i_wait_count=0;
    int *i_stat_loc = NULL ;
    void *pZero = 0;

    if(gettimeofday(&tp1,pZero) == -1)
	{
		perror("First: ");
		exit(0);
	}

   for(i=0;i<nProcess ;i++)
   {

      if((i_pid=fork())<0)
      {
        printf("\nFailed to execute instance %d\n",i_no_of_process);
        return(1);
      }
      else if(i_pid==0)
      {
        start_processing();
      }
      else
      {
       proc_id_A[i]=i_pid;
       i_no_of_process++;
      }
    }

   if(i == nProcess )
   {
     printf("\n\nNo of process initiated = %d",i_no_of_process);

     printf("\nSequence   Process Id      Wait Process Id    Status\n\n");

     for(i_wait_count=0;i_wait_count<i_no_of_process;i_wait_count++)
     {
       printf("%-8d   %ld   %21d   %9d\n",i_wait_count+1,proc_id_A[i_wait_count],
                                          waitpid(proc_id_A[i_wait_count],i_stat_loc ,WCONTINUED),i_stat_loc);
       if((i_stat_loc)!=0)
       {
         printf("Process [Id=%ld] has failed\n",proc_id_A[i_wait_count]);
         return(1);
       }
     }
   }

   if(gettimeofday(&tp2,pZero) == -1)
	{
		perror("Second: ");
		exit(0);
	}

     printf(" \n\nTHE TOTAL = %f",(float)(tp2.tv_sec - tp1.tv_sec) + ((float)(tp2.tv_usec - tp1.tv_usec)/1000000.0));
	printf("\n\nEnd Of Main Function\n");
}

void start_processing()
{
    int num_ret,total_records = 0,tot_recs_fetched=0,records_fetched;
    int not_complete = 1;

    while (*prt < (sizeof(records)/sizeof(record_log)))
	{
		get_transaction();
        C_INIT(filename);
        sprintf(filename,"%s_%d.out","child",trx->account_id);
        printf("\nfile name is : %s : %d %d",filename, getpid(),*prt);

        /* after creating file for each account, code will write account data in file */
    }
  printf("\n\nOut of  chield %d",getpid());
 exit(0);
}

fork.txt (2.4 KB)

anup13

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LEARN ABOUT MOJAVE

fork

FORK(2) 						      BSD System Calls Manual							   FORK(2)

NAME

     fork -- create a new process

SYNOPSIS

     #include <unistd.h>

     pid_t
     fork(void);

DESCRIPTION

     fork() causes creation of a new process.  The new process (child process) is an exact copy of the calling process (parent process) except for
     the following:

	   o   The child process has a unique process ID.

	   o   The child process has a different parent process ID (i.e., the process ID of the parent process).

	   o   The child process has its own copy of the parent's descriptors.	These descriptors reference the same underlying objects, so that,
	       for instance, file pointers in file objects are shared between the child and the parent, so that an lseek(2) on a descriptor in the
	       child process can affect a subsequent read or write by the parent.  This descriptor copying is also used by the shell to establish
	       standard input and output for newly created processes as well as to set up pipes.

	   o   The child processes resource utilizations are set to 0; see setrlimit(2).

RETURN VALUES

     Upon successful completion, fork() returns a value of 0 to the child process and returns the process ID of the child process to the parent
     process.  Otherwise, a value of -1 is returned to the parent process, no child process is created, and the global variable errno is set to
     indicate the error.

ERRORS

     fork() will fail and no child process will be created if:

     [EAGAIN]		The system-imposed limit on the total number of processes under execution would be exceeded.  This limit is configuration-
			dependent.

     [EAGAIN]		The system-imposed limit MAXUPRC (<sys/param.h>) on the total number of processes under execution by a single user would
			be exceeded.

     [ENOMEM]		There is insufficient swap space for the new process.

LEGACY SYNOPSIS

     #include <sys/types.h>
     #include <unistd.h>

     The include file <sys/types.h> is necessary.

SEE ALSO

     execve(2), sigaction(2), wait(2), compat(5)

HISTORY

     A fork() function call appeared in Version 6 AT&T UNIX.

CAVEATS

     There are limits to what you can do in the child process.	To be totally safe you should restrict yourself to only executing async-signal
     safe operations until such time as one of the exec functions is called.  All APIs, including global data symbols, in any framework or library
     should be assumed to be unsafe after a fork() unless explicitly documented to be safe or async-signal safe.  If you need to use these frame-
     works in the child process, you must exec.  In this situation it is reasonable to exec yourself.

4th Berkeley Distribution					   June 4, 1993 					 4th Berkeley Distribution