DevOps, CI/CD and Automation

Here is my question for Sun's C gurus:

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I want to copy the contents of a structure into
another instance of the same structure.

Example:

struct mystruct
{
char field1[20];
char field2 [30];
int field3;
};

Given two instances of this structure:

struct mystruct a;
struct mystruct b;

Careful way to copy contents of a into b would be:

strcpy(b.field1,a.field1);
strcpy(b.field2,a.field2);
b.field3 = a.field3;

But I have tried this method:

b = a;

Compiled under our Sun OS, this works fine.

Questions: Am I justified in treating structures
as "true" datatypes, like ints, etc? Can I be confident
that doing a value assignment like that above
will always work? How portable is this? Is it part
of ANSI C?

I want to know if I should really avoid structure
assignment like this in an application that must
be fairly robust, and portable.

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