| // Copyright (c) 2008, Google Inc. |
| // All rights reserved. |
| // |
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| // modification, are permitted provided that the following conditions are |
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| // distribution. |
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| // this software without specific prior written permission. |
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| // |
| // --- |
| // Author: Dave Nicponski |
| // |
| // Implement helpful bash-style command line flag completions |
| // |
| // ** Functional API: |
| // HandleCommandLineCompletions() should be called early during |
| // program startup, but after command line flag code has been |
| // initialized, such as the beginning of HandleCommandLineHelpFlags(). |
| // It checks the value of the flag --tab_completion_word. If this |
| // flag is empty, nothing happens here. If it contains a string, |
| // however, then HandleCommandLineCompletions() will hijack the |
| // process, attempting to identify the intention behind this |
| // completion. Regardless of the outcome of this deduction, the |
| // process will be terminated, similar to --helpshort flag |
| // handling. |
| // |
| // ** Overview of Bash completions: |
| // Bash can be told to programatically determine completions for the |
| // current 'cursor word'. It does this by (in this case) invoking a |
| // command with some additional arguments identifying the command |
| // being executed, the word being completed, and the previous word |
| // (if any). Bash then expects a sequence of output lines to be |
| // printed to stdout. If these lines all contain a common prefix |
| // longer than the cursor word, bash will replace the cursor word |
| // with that common prefix, and display nothing. If there isn't such |
| // a common prefix, bash will display the lines in pages using 'more'. |
| // |
| // ** Strategy taken for command line completions: |
| // If we can deduce either the exact flag intended, or a common flag |
| // prefix, we'll output exactly that. Otherwise, if information |
| // must be displayed to the user, we'll take the opportunity to add |
| // some helpful information beyond just the flag name (specifically, |
| // we'll include the default flag value and as much of the flag's |
| // description as can fit on a single terminal line width, as specified |
| // by the flag --tab_completion_columns). Furthermore, we'll try to |
| // make bash order the output such that the most useful or relevent |
| // flags are the most likely to be shown at the top. |
| // |
| // ** Additional features: |
| // To assist in finding that one really useful flag, substring matching |
| // was implemented. Before pressing a <TAB> to get completion for the |
| // current word, you can append one or more '?' to the flag to do |
| // substring matching. Here's the semantics: |
| // --foo<TAB> Show me all flags with names prefixed by 'foo' |
| // --foo?<TAB> Show me all flags with 'foo' somewhere in the name |
| // --foo??<TAB> Same as prior case, but also search in module |
| // definition path for 'foo' |
| // --foo???<TAB> Same as prior case, but also search in flag |
| // descriptions for 'foo' |
| // Finally, we'll trim the output to a relatively small number of |
| // flags to keep bash quiet about the verbosity of output. If one |
| // really wanted to see all possible matches, appending a '+' to the |
| // search word will force the exhaustive list of matches to be printed. |
| // |
| // ** How to have bash accept completions from a binary: |
| // Bash requires that it be informed about each command that programmatic |
| // completion should be enabled for. Example addition to a .bashrc |
| // file would be (your path to gflags_completions.sh file may differ): |
| |
| /* |
| $ complete -o bashdefault -o default -o nospace -C \ |
| '/usr/local/bin/gflags_completions.sh --tab_completion_columns $COLUMNS' \ |
| time env binary_name another_binary [...] |
| */ |
| |
| // This would allow the following to work: |
| // $ /path/to/binary_name --vmodule<TAB> |
| // Or: |
| // $ ./bin/path/another_binary --gfs_u<TAB> |
| // (etc) |
| // |
| // Sadly, it appears that bash gives no easy way to force this behavior for |
| // all commands. That's where the "time" in the above example comes in. |
| // If you haven't specifically added a command to the list of completion |
| // supported commands, you can still get completions by prefixing the |
| // entire command with "env". |
| // $ env /some/brand/new/binary --vmod<TAB> |
| // Assuming that "binary" is a newly compiled binary, this should still |
| // produce the expected completion output. |
| |
| |
| #ifndef GOOGLE_GFLAGS_COMPLETIONS_H_ |
| #define GOOGLE_GFLAGS_COMPLETIONS_H_ |
| |
| namespace google { |
| |
| void HandleCommandLineCompletions(void); |
| |
| } |
| |
| #endif // GOOGLE_GFLAGS_COMPLETIONS_H_ |
