c2efb3efcd
Revise docs for all "Scripting Commands", except four find_XXX that use a macro suite of their own. * Take full advantage of the improved syntax highlighting. * Make consequential use of <..> placeholders. * Clarify things here and there in the text. Specific improvements to some command docs: * "math": Correct description of novel hexadecimal capability. * "if", "foreach", "while": Provide link to "endif" etc * "foreach", "while": Mention "break" and "continue". * "foreach": Simplify explanation of ``RANGE`` and ``IN`` signatures; advise against negative arguments or reverse ranges (compare issue #18461) * "endif", "endfunction" etc: Explain that the argument is optional and maintained for compatibility only
33 lines
1.1 KiB
ReStructuredText
33 lines
1.1 KiB
ReStructuredText
unset
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-----
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Unset a variable, cache variable, or environment variable.
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.. code-block:: cmake
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unset(<variable> [CACHE | PARENT_SCOPE])
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Removes a normal variable from the current scope, causing it
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to become undefined. If ``CACHE`` is present, then a cache variable
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is removed instead of a normal variable. Note that when evaluating
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:ref:`Variable References` of the form ``${VAR}``, CMake first searches
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for a normal variable with that name. If no such normal variable exists,
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CMake will then search for a cache entry with that name. Because of this
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unsetting a normal variable can expose a cache variable that was previously
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hidden. To force a variable reference of the form ``${VAR}`` to return an
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empty string, use ``set(<variable> "")``, which clears the normal variable
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but leaves it defined.
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If ``PARENT_SCOPE`` is present then the variable is removed from the scope
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above the current scope. See the same option in the :command:`set` command
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for further details.
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``<variable>`` can be an environment variable such as:
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.. code-block:: cmake
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unset(ENV{LD_LIBRARY_PATH})
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in which case the variable will be removed from the current
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environment.
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