Return value (int) from main to calling shell

flounder · #1 (**permalink**) 09-25-2006

What is the sytax to return an int from C program main back to calling shell?

Code:

#!/usr/bin/ksh 

typeset -i NO_RECS

$NO_RECS=process_file

# Process file is a C program that is set up to return an int from main. The
#program complies with no issues, but an error is generated when the shell
#calls the program. Is the syntax correct to return the int value to a shell
#variable?

Here is the C program:

Code:

int main(argc,argv)
{

int no_recs_tot ;

/* This is just a function within the c program that returns the int value */

no_recs_tot = bld_detail(v_out_path,v_in_path,inrec_cnt,v_src_data_dt);
 
return (no_recs_tot);

} /* End main */

Corona688 · #2 (**permalink**) 09-25-2006

Code tags please. Like {code} int main(); {/code} but with [ ] instead of { }.

The syntax for returning a code to the shell is exactly as you show it. What might be wrong is the VALUE you return. Any non-zero value means some sort of error. Zero means success.

jim mcnamara · #3 (**permalink**) 09-25-2006

Plus, on a POSIX compliant system :

Code:

int main()
{
	return 42001;
}

Code:

$ cc -o testc test.c
$ testc
$echo $?
17

because 42001 % 512 = 17. There is a max value allowed for return codes. So, if the OP has several thousand records the value will be meaningless.

Return codes are for program status.

blowtorch · #4 (**permalink**) 09-25-2006

First of all,

Code:

#!/usr/bin/ksh 

typeset -i NO_RECS

$NO_RECS=process_file

Will not print the return code. The syntax is wrong to begin with, it should be

Code:

NO_RECS=$(process_file)

The second thing is that the return code of any command executed in the shell is not printed, but stored in a variable $?. To directly get the value that your C program has, you should do it like this:

Code:

#!/usr/bin/ksh
typeset -i NO_RECS
NO_RECS=$(process_file)

And your C program should be:

Code:

int main(argc,argv)
int argc; char *argv[];
{

int no_recs_tot ;

/* This is just a function within the c program that returns the int value */
no_recs_tot = bld_detail(v_out_path,v_in_path,inrec_cnt,v_src_data_dt);
 
fprintf(stdout,"%d",no_rec_tot);
} /* End main */

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