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<concept id="GUID-209F3620-2361-4AED-9F7A-02E72F9EE8FE" xml:lang="en"><title>Parent

and Child without IPC</title><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>In this scenario, the parent process creates the child, but there is no

subsequent communication between the two (except maybe the parent waiting

for termination of the child via use of the <xref href="GUID-8F5C89A4-7813-32C7-973E-F7F0F3690BC6.dita"><apiname>waitpid()</apiname></xref> function).</p>

<p>Rather than use the <codeph>fork()</codeph>/<codeph>exec()</codeph> combination

to achieve this the <xref href="GUID-E7C4DE71-BC5B-34AE-ACB3-C34A0DB1FC16.dita"><apiname>posix_spawn()</apiname></xref> API can be used instead.

This API will create a process by a single API call. Additionally, actions

can be performed on inherited file descriptors to change access before the

child's main is called. For more detailed information on the <xref href="GUID-E7C4DE71-BC5B-34AE-ACB3-C34A0DB1FC16.dita"><apiname>posix_spawn()</apiname></xref> function

consult the relevant Open Group standard pages available at <xref href="http://www.opengroup.org" scope="external">http:\\www.opengroup.org</xref>.</p>

<p><b>Parent process <codeph>fork()</codeph> and <codeph>exec()</codeph> functions</b></p>

<p>The following code shows how the creation of a child process can be implemented

using the <codeph>fork()</codeph> and <codeph>exec()</codeph> functions. Note

that inclusion of header files has been omitted for clarity. </p>

<codeblock xml:space="preserve">int main(int argc, char *argv[])

{

  pid_t Childpid = fork();

  if(Childpid == 0)

  {

      //Running in Child process

      //exec() to replace the child process executable

      char execFileName[] = "/root/PortDoc/Example0_c/Posix/child/ChildProg";

      execl(execFileName,NULL);

  }

  else

  {

     //Running in parent process

     //Wait for the child process to terminate

     waitpid(Childpid,NULL,0);

     printf("\r\n*** Child process finished ***\r\n");

  }

  return EXIT_SUCCESS;

}

</codeblock>

<p><b>Using the <codeph>posix_spawn()</codeph> function</b></p>

<p>The following code shows how the above can be modified to use the <codeph>posix_spawn()</codeph> operation.</p>

<codeblock xml:space="preserve">int main(int argc, char *argv[])

{

   pid_t Childpid;

   char execFileName[] = "/root/PortDoc/Example0_c/Symbian/child/ChildProg";

   int RetVal= posix_spawn(&Childpid,execFileName,NULL,NULL,NULL,NULL);

   (void)waitpid(Childpid,NULL,0);

   printf("\r\n*** Child process finished ***\r\n");

   return EXIT_SUCCESS;

}

</codeblock>

<p><b>Child process example</b></p>

<p>The child code shown is unaffected by the mechanism used to spawn it, that

is, <codeph>fork()</codeph>/<codeph>exec()</codeph> or <xref href="GUID-E7C4DE71-BC5B-34AE-ACB3-C34A0DB1FC16.dita"><apiname>posix_spawn()</apiname></xref>,

but an example is shown below for completeness.</p>

<codeblock xml:space="preserve">int main(void)

{

    printf("\r\n*** Child Running ***\r\n");

    return EXIT_SUCCESS;

}

</codeblock>