Passing return value from one main to other main function?

**GisiNA** · 05-13-2020

I wonder if it is possible to pass a return value from one main function as input value to another main function.

For example:

Program that passes a value:

Code:

//program-1.c

int main(void)
{
  return 10;
}

Program that receives the value returned by the previous program:

Code:

//program-2.c
#include <stdio.h>

int main(int argc, char* argv[])
{
  printf("%i", argv[1]);
}

On the console I wrote down:

Code:

program-1.c | program-2.c

But the output is 0, not 10.

Is it possible that program two returns the value 10 from program 1?
What must be done so that the return value of program 1 is received by program 2 and displayed on screen by printf ()?

**Salem** · 05-13-2020

> program-1.c | program-2.c
I assume you meant the compiled versions of the two programs.

Anyway, given this

Code:

int main(void)
{
  return 10;
}

You'll find your 10 in the exit status.

Code:

./program1
echo $?

> What must be done so that the return value of program 1 is received by program 2 and displayed on screen by printf ()?
Maybe...

Code:

./program1
echo $? | ./program2

**laserlight** · 05-13-2020

I suggest that you don't use the return value from main for this. Rather, write the value to standard output in the first program and read the value from standard input in the second program. Then invoke both programs such that the output of the first is piped as input to the second.

**GisiNA** · 05-14-2020

Thank you!

You're right, I was referring to placing

Code:

program-1.exe | program-2.exe

.
What I see is that the option you gives me is for linux (or Unix-based operating systems). Do you know what the command line for Windows would look like?

**GisiNA** · 05-14-2020

Thanks for the reply!
But my query is to know if there is a possibility of passing a returned value from one program to another program.
In other words, a main returns a value that is captured by another main.
Or if that possibility does not exist.

**john.c** · 05-14-2020

The return value from main is different from return values from other functions.
Main's return value is called the program's "exit status".
It is non-portable to use this value for anything but determining the success or failure of the program.
So in general, no, you cannot "return" a value from one program and use it in another.
There are many other ways for programs to communicate.
Pipes and the file system are perhaps the most common.

**laserlight** · 05-14-2020

Originally Posted by GisiNA

You're right, I was referring to placing

Code:

program-1.exe | program-2.exe

That is exactly what you would do to "invoke both programs such that the output of the first is piped as input to the second".

Originally Posted by GisiNA

But my query is to know if there is a possibility of passing a returned value from one program to another program.
In other words, a main returns a value that is captured by another main.
Or if that possibility does not exist.

According to your previous post, you're asking asking about how to implement programs such that you can pipe I/O, so what I described about one program printing to standard output and the other program reading from standard input is exactly what you should do.

**Salem** · 05-14-2020

> Do you know what the command line for Windows would look like?
Errorlevel - Windows CMD - SS64.com
But be prepared for even more crustyness.

**GisiNA** · 05-25-2020

Thanks to all for the answers!!!!

Thread: Passing return value from one main to other main function?

Thread Tools

Search Thread

Display

Passing return value from one main to other main function?

Similar Threads

works fine upto k=2 in main . k=3 in main after mergelen>66 free function gives error

How to use a function that doesn't return a value in main()? Is it even possible?

return 0 to main from within a function, is this possible?

Any way to return to the top of main from a function

getting a function to return to main??

Tags for this Thread