122 lines
5.6 KiB
C++
122 lines
5.6 KiB
C++
// Copyright (c) 2008, Google Inc.
|
|
// All rights reserved.
|
|
//
|
|
// Redistribution and use in source and binary forms, with or without
|
|
// modification, are permitted provided that the following conditions are
|
|
// met:
|
|
//
|
|
// * Redistributions of source code must retain the above copyright
|
|
// notice, this list of conditions and the following disclaimer.
|
|
// * Redistributions in binary form must reproduce the above
|
|
// copyright notice, this list of conditions and the following disclaimer
|
|
// in the documentation and/or other materials provided with the
|
|
// distribution.
|
|
// * Neither the name of Google Inc. nor the names of its
|
|
// contributors may be used to endorse or promote products derived from
|
|
// this software without specific prior written permission.
|
|
//
|
|
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
|
|
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
|
|
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
|
|
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
|
|
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
|
|
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
|
|
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
|
|
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
|
|
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
|
|
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
//
|
|
// ---
|
|
|
|
//
|
|
// 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 \
|
|
'/home/build/eng/bash/bash_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 GFLAGS_COMPLETIONS_H_
|
|
#define GFLAGS_COMPLETIONS_H_
|
|
|
|
namespace gflags {
|
|
|
|
extern void HandleCommandLineCompletions(void);
|
|
|
|
}
|
|
|
|
#endif // GFLAGS_COMPLETIONS_H_
|