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Full Discussion: Function main returning int?
Top Forums Programming Function main returning int? Post 302727113 by jim mcnamara on Monday 5th of November 2012 08:07:54 PM
Old 11-05-2012
Read the main page on waitpid or wait to get more detail.

The return value of a process to the calling is process is the least significant eight bits of the number returned by main(). Which can be seen as signed or unsigned by the parent. So, the valid results from calling wait on a child returns values from 0 to 255 (looked at as unsigned).

By convention 0 means success, as defined in C by EXIT_SUCCESS.

Since main() is an int function you can return any valid int, but is not very useful to return numbers larger than the range I just defined.

Code:
// retval.c
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char **argv)
{
     int retval=atoi(argv[1]);
     printf("I am returning %d\n", retval);
     return retval;
}

Compile retval then run it with this script
Code:
#!/bin/ksh
cnt=1
while [ $cnt -le 100000000 ]
do
       retval $cnt
       cnt=$((  $cnt * 10 ))
done

And see what happens...
 

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LEARN ABOUT CENTOS

papi_attach

PAPI_attach(3)							       PAPI							    PAPI_attach(3)

NAME

       PAPI_attach -

       Attach PAPI event set to the specified thread id.

SYNOPSIS

Detailed Description
       @par C Interface:
       int PAPI_attach( int EventSet, unsigned long tid );

       PAPI_attach is a wrapper function that calls PAPI_set_opt to allow PAPI to
       monitor performance counts on a thread other than the one currently executing.
       This is sometimes referred to as third party monitoring.
       PAPI_attach connects the specified EventSet to the specifed thread;
       PAPI_detach breaks that connection and restores the EventSet to the
       original executing thread.

       @param EventSet
	   An integer handle for a PAPI EventSet as created by PAPI_create_eventset.
       @param tid
	   A thread id as obtained from, for example, PAPI_list_threads or PAPI_thread_id.

       @retval PAPI_ECMP
	   This feature is unsupported on this component.
       @retval PAPI_EINVAL
	   One or more of the arguments is invalid.
       @retval PAPI_ENOEVST
	   The event set specified does not exist.
       @retval PAPI_EISRUN
	   The event set is currently counting events.

       @par Examples:

       *   int EventSet = PAPI_NULL;
       *   unsigned long pid;
       *   pid = fork( );
       *   if ( pid <= 0 )
       *   exit( 1 );
       *   if ( PAPI_create_eventset( &EventSet ) != PAPI_OK )
       *   exit( 1 );
       *   // Add Total Instructions Executed to our EventSet
       *   if ( PAPI_add_event( EventSet, PAPI_TOT_INS ) != PAPI_OK )
       *   exit( 1 );
       *   // Attach this EventSet to the forked process
       *   if ( PAPI_attach( EventSet, pid ) != PAPI_OK )
       *   exit( 1 );
       *

       See Also:
	   PAPI_set_opt

	   PAPI_list_threads

	   PAPI_thread_id

	   PAPI_thread_init

Author
       Generated automatically by Doxygen for PAPI from the source code.

Version 5.2.0.0 						  Tue Jun 17 2014						    PAPI_attach(3)
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