Shell Programming and Scripting

It seems $? can only contain one byte. see below:

Code:

int main()
{
       return 0x12345678;
}

After I run the code and check the $? value it output 120, obviously it is the decimal of the last byte of 0x12345678. And if I return a value less than 255, the $? value seems right.

Why? and if $? can only contain one byte how to get the real return value of main() ? thx.

While main() may return an int, I believe the valid range is 0-255 as far as most shells are concerned. I know ksh93 uses only the least significant 8 bits.

The shell will only keep an unsigned byte in the status return value (values 0...255). It takes the exit value and just looks at that last byte.
The exit/return code is to be able to signal success or failure of a program not for regular output.

To get the output of your program you should write the output to stdout and capture it with something like:

Code:

output=$(/path/Your_Program)

or:

Code:

/path/Your_Program | while read line
do
  ...
done

Thank you very much.