summaryrefslogtreecommitdiffstats
path: root/doc/user/help.in
blob: 4356d18c29c2bdef7cea312be215d300a59e9514 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
<!--

  __COPYRIGHT__

  Permission is hereby granted, free of charge, to any person obtaining
  a copy of this software and associated documentation files (the
  "Software"), to deal in the Software without restriction, including
  without limitation the rights to use, copy, modify, merge, publish,
  distribute, sublicense, and/or sell copies of the Software, and to
  permit persons to whom the Software is furnished to do so, subject to
  the following conditions:

  The above copyright notice and this permission notice shall be included
  in all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
  KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
  WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

-->

   <para>

   It's often very useful to be able to give
   users some help that describes the
   specific targets, build options, etc.,
   that can be used for your build.
   &SCons; provides the &Help; function
   to allow you to specify this help text:

   </para>

   <scons_example name="ex1">
      <file name="SConstruct" printme="1">
      Help("""
      Type: 'scons program' to build the production program,
            'scons debug' to build the debug version.
      """)
      </file>
   </scons_example>

   <para>

   (Note the above use of the Python triple-quote syntax,
   which comes in very handy for
   specifying multi-line strings like help text.)

   </para>

   <para>

   When the &SConstruct; or &SConscript; files
   contain such a call to the &Help; function,
   the specified help text will be displayed in response to
   the &SCons; <literal>-h</literal> option:

   </para>

   <scons_output example="ex1">
      <scons_output_command>scons -h</scons_output_command>
   </scons_output>

   <para>

   The &SConscript; files may contain
   multiple calls to the &Help; function,
   in which case the specified text(s)
   will be concatenated when displayed.
   This allows you to split up the
   help text across multiple &SConscript; files.
   In this situation, the order in
   which the &SConscript; files are called
   will determine the order in which the &Help; functions are called,
   which will determine the order in which
   the various bits of text will get concatenated.

   </para>

   <para>

   Another use would be to make the help text conditional
   on some variable.
   For example, suppose you only want to display
   a line about building a Windows-only
   version of a program when actually
   run on Windows.
   The following &SConstruct; file:

   </para>

   <scons_example name="ex2">
      <file name="SConstruct" printme="1">
      env = Environment()

      Help("\nType: 'scons program' to build the production program.\n")

      if env['PLATFORM'] == 'win32':
          Help("\nType: 'scons windebug' to build the Windows debug version.\n")
      </file>
   </scons_example>

   <para>

   Will display the completely help text on Windows:

   </para>

   <scons_output example="ex2" os="win32">
      <scons_output_command>scons -h</scons_output_command>
   </scons_output>

   <para>

   But only show the relevant option on a Linux or UNIX system:

   </para>

   <scons_output example="ex2" os="posix">
      <scons_output_command>scons -h</scons_output_command>
   </scons_output>

   <para>

   If there is no &Help; text in the &SConstruct; or
   &SConscript; files,
   &SCons; will revert to displaying its
   standard list that describes the &SCons; command-line
   options.
   This list is also always displayed whenever
   the <literal>-H</literal> option is used.

   </para>