UNIX Programming and Technical

Q. How can a parent and child process communicate?

A. A parent and child can communicate through any of the normal inter-process communication schemes (pipes, sockets, message queues, shared memory), but also have some special ways to communicate that take advantage of their relationship as a parent and child. One of the most obvious is that the parent can get the exit status of the child.

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UNIX Other Question

Q. How can you get/set an environment variable from a program?

A. Getting the value of an environment variable is done by using `getenv()'.
Setting the value of an environment variable is done by using `putenv()'. Q. What is a zombie?

A. When a program forks and the child finishes before the parent, the kernel still keeps some of its information about the child in case the parent might need it - for example, the parent may need to check the child's exit status. To be able to get this information, the parent calls `wait()'; In the interval between the child terminating and the parent calling `wait()', the child is said to be a `zombie' (If you do `ps', the child will have a `Z' in its status field to indicate this.)