How can a process change an environment variable in its caller?
It may or may not be possible to do so at all. Different operating systems implement global name/value functionality similar to the Unix environment in different ways. Whether the ``environment'' can be usefully altered by a running program, and if so, how, is system-dependent.
Under Unix, a process can modify its own environment (some systems provide setenv or putenv functions for the purpose), and the modified environment is generally passed on to child processes, but it is not propagated back to the parent process.
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This page by Steve Summit // Copyright 1995 // mail feedback