/thirdparty/breakpad/third_party/linux/include/gflags/gflags_completions.h

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 29//
 30// ---
 31// Author: Dave Nicponski
 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 '/usr/local/bin/gflags_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 GOOGLE_GFLAGS_COMPLETIONS_H_
113#define GOOGLE_GFLAGS_COMPLETIONS_H_
114
115namespace google {
116
117void HandleCommandLineCompletions(void);
118
119}
120
121#endif  // GOOGLE_GFLAGS_COMPLETIONS_H_