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// Copyright (c) 2008, Google Inc.
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// All rights reserved.
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following disclaimer
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// in the documentation and/or other materials provided with the
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived from
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// this software without specific prior written permission.
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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// Author: Dave Nicponski
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// Implement helpful bash-style command line flag completions
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// HandleCommandLineCompletions() should be called early during
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// program startup, but after command line flag code has been
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// initialized, such as the beginning of HandleCommandLineHelpFlags().
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// It checks the value of the flag --tab_completion_word. If this
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// flag is empty, nothing happens here. If it contains a string,
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// however, then HandleCommandLineCompletions() will hijack the
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// process, attempting to identify the intention behind this
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// completion. Regardless of the outcome of this deduction, the
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// process will be terminated, similar to --helpshort flag
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// ** Overview of Bash completions:
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// Bash can be told to programatically determine completions for the
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// current 'cursor word'. It does this by (in this case) invoking a
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// command with some additional arguments identifying the command
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// being executed, the word being completed, and the previous word
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// (if any). Bash then expects a sequence of output lines to be
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// printed to stdout. If these lines all contain a common prefix
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// longer than the cursor word, bash will replace the cursor word
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// with that common prefix, and display nothing. If there isn't such
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// a common prefix, bash will display the lines in pages using 'more'.
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// ** Strategy taken for command line completions:
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// If we can deduce either the exact flag intended, or a common flag
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// prefix, we'll output exactly that. Otherwise, if information
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// must be displayed to the user, we'll take the opportunity to add
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// some helpful information beyond just the flag name (specifically,
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// we'll include the default flag value and as much of the flag's
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// description as can fit on a single terminal line width, as specified
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// by the flag --tab_completion_columns). Furthermore, we'll try to
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// make bash order the output such that the most useful or relevent
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// flags are the most likely to be shown at the top.
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// ** Additional features:
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// To assist in finding that one really useful flag, substring matching
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// was implemented. Before pressing a <TAB> to get completion for the
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// current word, you can append one or more '?' to the flag to do
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// substring matching. Here's the semantics:
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// --foo<TAB> Show me all flags with names prefixed by 'foo'
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// --foo?<TAB> Show me all flags with 'foo' somewhere in the name
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// --foo??<TAB> Same as prior case, but also search in module
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// definition path for 'foo'
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// --foo???<TAB> Same as prior case, but also search in flag
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// descriptions for 'foo'
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// Finally, we'll trim the output to a relatively small number of
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// flags to keep bash quiet about the verbosity of output. If one
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// really wanted to see all possible matches, appending a '+' to the
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// search word will force the exhaustive list of matches to be printed.
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// ** How to have bash accept completions from a binary:
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// Bash requires that it be informed about each command that programmatic
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// completion should be enabled for. Example addition to a .bashrc
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// file would be (your path to gflags_completions.sh file may differ):
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$ complete -o bashdefault -o default -o nospace -C \
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'/usr/local/bin/gflags_completions.sh --tab_completion_columns $COLUMNS' \
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time env binary_name another_binary [...]
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// This would allow the following to work:
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// $ /path/to/binary_name --vmodule<TAB>
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// $ ./bin/path/another_binary --gfs_u<TAB>
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// Sadly, it appears that bash gives no easy way to force this behavior for
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// all commands. That's where the "time" in the above example comes in.
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// If you haven't specifically added a command to the list of completion
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// supported commands, you can still get completions by prefixing the
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// entire command with "env".
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// $ env /some/brand/new/binary --vmod<TAB>
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// Assuming that "binary" is a newly compiled binary, this should still
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// produce the expected completion output.
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#ifndef GOOGLE_GFLAGS_COMPLETIONS_H_
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#define GOOGLE_GFLAGS_COMPLETIONS_H_
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// Annoying stuff for windows -- makes sure clients can import these functions
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#ifndef GFLAGS_DLL_DECL
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# define GFLAGS_DLL_DECL __declspec(dllimport)
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# define GFLAGS_DLL_DECL
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GFLAGS_DLL_DECL void HandleCommandLineCompletions(void);
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#endif // GOOGLE_GFLAGS_COMPLETIONS_H_