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1 // Copyright (c) 2008, Google Inc. | |
2 // All rights reserved. | |
3 // | |
4 // Redistribution and use in source and binary forms, with or without | |
5 // modification, are permitted provided that the following conditions are | |
6 // met: | |
7 // | |
8 // * Redistributions of source code must retain the above copyright | |
9 // notice, this list of conditions and the following disclaimer. | |
10 // * Redistributions in binary form must reproduce the above | |
11 // copyright notice, this list of conditions and the following disclaimer | |
12 // in the documentation and/or other materials provided with the | |
13 // distribution. | |
14 // * Neither the name of Google Inc. nor the names of its | |
15 // contributors may be used to endorse or promote products derived from | |
16 // this software without specific prior written permission. | |
17 // | |
18 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |
19 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |
20 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | |
21 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | |
22 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |
23 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | |
24 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
25 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
26 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
27 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | |
28 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
29 // | |
30 // --- | |
31 | |
32 // | |
33 // Implement helpful bash-style command line flag completions | |
34 // | |
35 // ** Functional API: | |
36 // HandleCommandLineCompletions() should be called early during | |
37 // program startup, but after command line flag code has been | |
38 // initialized, such as the beginning of HandleCommandLineHelpFlags(). | |
39 // It checks the value of the flag --tab_completion_word. If this | |
40 // flag is empty, nothing happens here. If it contains a string, | |
41 // however, then HandleCommandLineCompletions() will hijack the | |
42 // process, attempting to identify the intention behind this | |
43 // completion. Regardless of the outcome of this deduction, the | |
44 // process will be terminated, similar to --helpshort flag | |
45 // handling. | |
46 // | |
47 // ** Overview of Bash completions: | |
48 // Bash can be told to programatically determine completions for the | |
49 // current 'cursor word'. It does this by (in this case) invoking a | |
50 // command with some additional arguments identifying the command | |
51 // being executed, the word being completed, and the previous word | |
52 // (if any). Bash then expects a sequence of output lines to be | |
53 // printed to stdout. If these lines all contain a common prefix | |
54 // longer than the cursor word, bash will replace the cursor word | |
55 // with that common prefix, and display nothing. If there isn't such | |
56 // a common prefix, bash will display the lines in pages using 'more'. | |
57 // | |
58 // ** Strategy taken for command line completions: | |
59 // If we can deduce either the exact flag intended, or a common flag | |
60 // prefix, we'll output exactly that. Otherwise, if information | |
61 // must be displayed to the user, we'll take the opportunity to add | |
62 // some helpful information beyond just the flag name (specifically, | |
63 // we'll include the default flag value and as much of the flag's | |
64 // description as can fit on a single terminal line width, as specified | |
65 // by the flag --tab_completion_columns). Furthermore, we'll try to | |
66 // make bash order the output such that the most useful or relevent | |
67 // flags are the most likely to be shown at the top. | |
68 // | |
69 // ** Additional features: | |
70 // To assist in finding that one really useful flag, substring matching | |
71 // was implemented. Before pressing a <TAB> to get completion for the | |
72 // current word, you can append one or more '?' to the flag to do | |
73 // substring matching. Here's the semantics: | |
74 // --foo<TAB> Show me all flags with names prefixed by 'foo' | |
75 // --foo?<TAB> Show me all flags with 'foo' somewhere in the name | |
76 // --foo??<TAB> Same as prior case, but also search in module | |
77 // definition path for 'foo' | |
78 // --foo???<TAB> Same as prior case, but also search in flag | |
79 // descriptions for 'foo' | |
80 // Finally, we'll trim the output to a relatively small number of | |
81 // flags to keep bash quiet about the verbosity of output. If one | |
82 // really wanted to see all possible matches, appending a '+' to the | |
83 // search word will force the exhaustive list of matches to be printed. | |
84 // | |
85 // ** How to have bash accept completions from a binary: | |
86 // Bash requires that it be informed about each command that programmatic | |
87 // completion should be enabled for. Example addition to a .bashrc | |
88 // file would be (your path to gflags_completions.sh file may differ): | |
89 | |
90 /* | |
91 $ complete -o bashdefault -o default -o nospace -C \ | |
92 '/home/build/eng/bash/bash_completions.sh --tab_completion_columns $COLUMNS' \ | |
93 time env binary_name another_binary [...] | |
94 */ | |
95 | |
96 // This would allow the following to work: | |
97 // $ /path/to/binary_name --vmodule<TAB> | |
98 // Or: | |
99 // $ ./bin/path/another_binary --gfs_u<TAB> | |
100 // (etc) | |
101 // | |
102 // Sadly, it appears that bash gives no easy way to force this behavior for | |
103 // all commands. That's where the "time" in the above example comes in. | |
104 // If you haven't specifically added a command to the list of completion | |
105 // supported commands, you can still get completions by prefixing the | |
106 // entire command with "env". | |
107 // $ env /some/brand/new/binary --vmod<TAB> | |
108 // Assuming that "binary" is a newly compiled binary, this should still | |
109 // produce the expected completion output. | |
110 | |
111 | |
112 #ifndef GFLAGS_COMPLETIONS_H_ | |
113 #define GFLAGS_COMPLETIONS_H_ | |
114 | |
115 namespace google { | |
116 | |
117 extern void HandleCommandLineCompletions(void); | |
118 | |
119 } | |
120 | |
121 #endif // GFLAGS_COMPLETIONS_H_ | |
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