Collecting value returned by main()

[vpawizard]

Hello,
Is it possible to store the value returned by main() into a variable? I have an executable which takes two values as arguments and returns the sum. I invoke the executable from another program which subsequently uses the returned values(sum of two numbers). I am programming in Unix environment.

Thanks in advance.

[r035198x]

Hello,
Is it possible to store the value returned by main() into a variable? I have an executable which takes two values as arguments and returns the sum. I invoke the executable from another program which subsequently uses the returned values(sum of two numbers). I am programming in Unix environment.

Thanks in advance.

Hi vp,

How are you invoking the other program? (If you could post the codes you are using).

[horace1]

Hello,
Is it possible to store the value returned by main() into a variable? I have an executable which takes two values as arguments and returns the sum. I invoke the executable from another program which subsequently uses the returned values(sum of two numbers). I am programming in Unix environment.

Thanks in advance.

if you are using swawnlp() to run the child process
http://www.qnx.com/developers/docs/momentics621_docs/neutrino/lib_ref/s/spawnl.html

with mode P_WAIT (parent waits for child to terminate) spawnlp() returns the exit status of the child process

[vpawizard]

I tried the following but still getting PID of child:

Code for mainprg.c:

 
#include <unistd.h>
#include <stdio.h>
#include <process.h>
 
int main()
{
        char num1[]="20";
        char num2[]="30";
        int wait_status;
 
        wait_status=spawnl(1,"./arithmetic.exe",num1,num2,(char*)NULL);
        printf("%d\n",wait_status);
 
        return 0;
}
 
 

Code for arithmetic.c:

 
 
#include <unistd.h>
#include <stdlib.h>
#include <math.h>
 
int main(int argc,char* argv[])
{
        exit(atoi(argv[0]) + atoi(argv[1]));
}
 
 

[horace1]

I tried the following but still getting PID of child:

Code for mainprg.c:

        wait_status=spawnl(1,"./arithmetic.exe",num1,num2,(char*)NULL);
 
 

the first parameter of spawnlp() is 1 which is probably P_NOWAIT - the value returned by P_NOWAIT is the PID of the child process. To get the exit status for a P_NOWAIT process, you must use the waitpid() function, giving it this process ID.

Do you need the child to run concurrently with the parent? - if not use P_WAIT which waits for the child to complete then returns the exit status of the child process.

[vpawizard]

/usr/include/process.h :

#define _P_WAIT 1
#define _P_NOWAIT 2
#define _P_OVERLAY 3
#define _P_NOWAITO 4
#define _P_DETACH 5

[vpawizard]

Here are some sample runs of my program:

$ ./mainprg
Enter first number:123
Enter second number:127
In arithmetic.c,main():250
In mainprg.c,wait_status:64000

$ ./mainprg
Enter first number:452
Enter second number:123
In arithmetic.c,main():575
In mainprg.c,wait_status:16128


$ ./mainprg
Enter first number:123
Enter second number:127
In arithmetic.c,main():250
In mainprg.c,wait_status:64000

$ ./mainprg
Enter first number:10
Enter second number:20
In arithmetic.c,main():30
In mainprg.c,wait_status:7680

$ ./mainprg
Enter first number:452
Enter second number:123
In arithmetic.c,main():575
In mainprg.c,wait_status:16128

Please note the output for the set of input !!!

[vpawizard]

Hello,
Thanks for help. I found out the problem:

If the parent process of the calling process is running a wait call, it is notified of the termination of the calling process and the low-order 8 bits (that is, bits 0377 or 0xFF) of the Status parameter are made available to it.