1 /*============================================================================
2 CMake - Cross Platform Makefile Generator
3 Copyright 2000-2009 Kitware, Inc., Insight Software Consortium
5 Distributed under the OSI-approved BSD License (the "License");
6 see accompanying file Copyright.txt for details.
8 This software is distributed WITHOUT ANY WARRANTY; without even the
9 implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
10 See the License for more information.
11 ============================================================================*/
12 #ifndef cmSetCommand_h
13 #define cmSetCommand_h
15 #include "cmCommand.h"
17 /** \class cmSetCommand
18 * \brief Set a CMAKE variable
20 * cmSetCommand sets a variable to a value with expansion.
22 class cmSetCommand : public cmCommand
26 * This is a virtual constructor for the command.
28 virtual cmCommand* Clone()
30 return new cmSetCommand;
34 * This is called when the command is first encountered in
35 * the CMakeLists.txt file.
37 virtual bool InitialPass(std::vector<std::string> const& args,
38 cmExecutionStatus &status);
41 * This determines if the command is invoked when in script mode.
43 virtual bool IsScriptable() const { return true; }
46 * The name of the command as specified in CMakeList.txt.
48 virtual const char* GetName() const {return "set";}
51 * Succinct documentation.
53 virtual const char* GetTerseDocumentation() const
55 return "Set a CMake, cache or environment variable to a given value.";
61 virtual const char* GetFullDocumentation() const
64 " set(<variable> <value>\n"
65 " [[CACHE <type> <docstring> [FORCE]] | PARENT_SCOPE])\n"
66 "Within CMake sets <variable> to the value <value>. "
67 "<value> is expanded before <variable> is set to it. "
68 "Normally, set will set a regular CMake variable. "
69 "If CACHE is present, then the <variable> is put in the cache "
70 "instead, unless it is already in the cache. "
71 "See section 'Variable types in CMake' below for details of "
72 "regular and cache variables and their interactions. "
73 "If CACHE is used, <type> and <docstring> are required. <type> is used "
74 "by the CMake GUI to choose a widget with which the user sets a value. "
75 "The value for <type> may be one of\n"
76 " FILEPATH = File chooser dialog.\n"
77 " PATH = Directory chooser dialog.\n"
78 " STRING = Arbitrary string.\n"
79 " BOOL = Boolean ON/OFF checkbox.\n"
80 " INTERNAL = No GUI entry (used for persistent variables).\n"
81 "If <type> is INTERNAL, the cache variable is marked as internal, "
82 "and will not be shown to the user in tools like cmake-gui. "
83 "This is intended for values that should be persisted in the cache, "
84 "but which users should not normally change. INTERNAL implies FORCE."
86 "Normally, set(...CACHE...) creates cache variables, but does not "
88 "If FORCE is specified, the value of the cache variable is set, even "
89 "if the variable is already in the cache. This should normally be "
90 "avoided, as it will remove any changes to the cache variable's value "
92 "If PARENT_SCOPE is present, the variable will be set in the scope "
93 "above the current scope. Each new directory or function creates a new "
94 "scope. This command will set the value of a variable into the parent "
95 "directory or calling function (whichever is applicable to the case at "
96 "hand). PARENT_SCOPE cannot be combined with CACHE.\n"
97 "If <value> is not specified then the variable is removed "
98 "instead of set. See also: the unset() command.\n"
99 " set(<variable> <value1> ... <valueN>)\n"
100 "In this case <variable> is set to a semicolon separated list of "
102 "<variable> can be an environment variable such as:\n"
103 " set( ENV{PATH} /home/martink )\n"
104 "in which case the environment variable will be set.\n"
105 "*** Variable types in CMake ***\n"
106 "In CMake there are two types of variables: normal variables and cache "
107 "variables. Normal variables are meant for the internal use of the "
108 "script (just like variables in most programming languages); they are "
109 "not persisted across CMake runs. "
110 "Cache variables (unless set with INTERNAL) are mostly intended for "
111 "configuration settings where the first CMake run determines a "
112 "suitable default value, which the user can then override, by editing "
113 "the cache with tools such as ccmake or cmake-gui. "
114 "Cache variables are stored in the CMake cache file, and "
115 "are persisted across CMake runs. \n"
116 "Both types can exist at the same time with the same name "
117 "but different values. "
118 "When ${FOO} is evaluated, CMake first looks for "
119 "a normal variable 'FOO' in scope and uses it if set. "
120 "If and only if no normal variable exists then it falls back to the "
121 "cache variable 'FOO'.\n"
123 "The code 'set(FOO \"x\")' sets the normal variable 'FOO'. It does not "
124 "touch the cache, but it will hide any existing cache value 'FOO'.\n"
125 "The code 'set(FOO \"x\" CACHE ...)' checks for 'FOO' in the cache, "
126 "ignoring any normal variable of the same name. If 'FOO' is in the "
127 "cache then nothing happens to either the normal variable or the cache "
128 "variable. If 'FOO' is not in the cache, then it is added to the "
130 "Finally, whenever a cache variable is added or modified by a command, "
131 "CMake also *removes* the normal variable of the same name from the "
132 "current scope so that an immediately following evaluation of "
133 "it will expose the newly cached value.\n"
134 "Normally projects should avoid using normal and cache variables of "
135 "the same name, as this interaction can be hard to follow. "
136 "However, in some situations it can be useful. "
137 "One example (used by some projects):"
139 "A project has a subproject in its source tree. The child project has "
140 "its own CMakeLists.txt, which is included from the parent "
141 "CMakeLists.txt using add_subdirectory(). "
142 "Now, if the parent and the child project provide the same option "
143 "(for example a compiler option), the parent gets the first chance "
144 "to add a user-editable option to the cache. "
145 "Normally, the child would then use the same value "
146 "that the parent uses. "
147 "However, it may be necessary to hard-code the value for the child "
148 "project's option while still allowing the user to edit the value used "
149 "by the parent project. The parent project can achieve this simply by "
150 "setting a normal variable with the same name as the option in a scope "
151 "sufficient to hide the option's cache variable from the child "
152 "completely. The parent has already set the cache variable, so the "
153 "child's set(...CACHE...) will do nothing, and evaluating the option "
154 "variable will use the value from the normal variable, which hides the "
158 cmTypeMacro(cmSetCommand, cmCommand);