Child process is not getting started

Crab · #1 (**permalink**) 09-16-2006

Hi,
When i m trying to run below code,its entering into wait stage.

output: In parent
pid=2134 // some random value assigned to child process
parent waiting.....

and then it keeps on waiting for child to get terminate

Y this child is not getting started....atleast i should get " ---in child"

Code:


printf("In parent");
for(i=0;i<3;i++)
	{	
	  pid=fork();
          printf("pid= %d",pid);
	  if(pid==0)
		{
		  printf("---in child");
		  memset(temp,0,100);
		  strcpy(temp,commandList[i]);
		  intial_command=strtok(temp," ,\0,");
  
		  if(i==0)
		   {
				close(1);
				dup2(pipes[0][0],1);
				close(pipes[0][1]);
				execvp(intial_command,commandList[i]);
			}
		  else
			{
			  if(i==countCommands-1)
				{
					close(0);
					dup2(pipes[i][1],0);
					close(pipes[i][0]);
					execvp(intial_command,commandList[i]);
				}
			  else
				{
				  close(0);
				  dup2(pipes[i][1],0);
				  close(1);
				  dup2(pipes[i][0],1);
				  execvp(intial_command,commandList[i]);
				}
			}
		}
		printf("parent waiting.....");
		waitpid(pid,&processStatus,0);
	}

..pls help me out...its bit urgent

matrixmadhan · #2 (**permalink**) 09-16-2006

please use code tags ...

you are checking only with pid == 0
what if the system (kernel) has failed to fork a process ?

check the condition if pid < 0 also

check from ps -ef that both parent and child are running !!!

Crab · #3 (**permalink**) 09-16-2006

i tried to check which all processes are running....actaully both child and parent processes are running...but its not entering into child's code

matrixmadhan · #4 (**permalink**) 09-17-2006

i doubt here

Code:

printf("---in child");

since the buffer is not filled with just '---in child'
and the printf is not directed to flush immediately
i think it is delayed...

try as

Code:

printf("---in child\n");

jenmead · #5 (**permalink**) 09-17-2006

You really need to check the return from your fork, like for instance:

fork_return = fork();
if( fork_return < 0)
{
curtime = time (NULL); /* get current time */
loctime = localtime (&curtime);
fprintf(fplog,"Unable to spawn child process, exiting. ");
fputs (asctime (loctime), fplog);
fprintf(fplog, "errno: %s\n",strerror(errno));
exit(-1);
}

Add in errno.h and then look at the errno string. Good luck,
Jen

Crab · #6 (**permalink**) 09-17-2006

by using printf("--in child\n") instead of printf("--in child") , i got the desired output

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