Programming

Originally Posted by agama

Great progress!

You need to correct a few things if you haven't.

First, the warning about %s in conjunction with strerror() is because you haven't included string.h. The strerror() function returns a pointer to a string, and if you don't include string.h the compiler assumes that it returns int, and thus issues the warning about the mismatch with %s. Include string.h and change the %d to a %s. It has nothing to do with the type of errno.

You also should include sys/types.h and sys/wait.h.

Your initialisation of a, b and c is missing curly braces. To be correct, you need something like this for a and b:

Code:

int a[2][3] = { {1,2,3},
                   {4,5,6} };

For c you need

Code:

int c[2][4] = { {0}, {0} };

Those are all to correct compiler warnings. The real problem is in your writing from the child. You are converting each value to string and placing it in str with a terminating NULL character. That is correct. However, you are writing the entire buffer, including the characters past the NULL to the parent. You need to write just the values, and the associated trailing blank, to the parent. To do this you need to capture the length of the string created by sprintf() and use that as the number of characters to write to the pipe. For completeness, I would also write a final NULL to the pipe after all of the values. Something like the code segment below:

Code:

                    len = sprintf( str, "%d ", c[i][j] );   // length of value+blank into len
                    w = write( pipefd[1], str, len  );     // write only the value and blank
                    if( w != len )                         // check the number written, not the size of str
                        printf("\nWrite error");        // maybe exit too?
            }
            *str = 0;                     // write a final NULL to terminate the string
            write( pipefd[1], str, 1 );
            exit(0);