Provided by: libbobcat-dev_6.02.02-1_amd64 
NAME
FBB::ReadLineBuf - std::streambuf offering line-editing and history
SYNOPSIS
#include <bobcat/readlinebuf>
Linking option: -lbobcat -lreadline
DESCRIPTION
The FBB::ReadLineBuf object may be used as a std::streambuf of std::istream objects,
allowing line-editing and history manipulation.
The ReadLineBuf class uses Gnu’s readline library to allow editing of input lines. The
ReadLineBuf object can be used to construct a std::istream allowing in-line editing of
lines read from the terminal. All lines may be preceded by a configurable prompt.
Since Gnu’s readline library operates on global data there can only be one ReadLineBuf
object. Therefore ReadLineBuf is a singleton class: in any program there can only be one
ReadLineBuf object (Gnu’s readline library does, however, offer functions allowing
programs to use multiple histories. So it would in principle be possible to design a
non-singleton ReadLineBuf class. Since programs normally only interact with a single
terminal, there is probably little use for non-singleton ReadLineBuf class).
ReadLineBuf offers editing capabilities while the user is entering lines. Like Gnu’s
readline(3) function, the line editing commands are by default similar to those of
emacs(1), but can easily be reconfigured, e.g. to offer vi(1)-like characteristics.
History manipulation is provided as an option. The collected history may be accessed for
reading using an FBB::ReadLineHistory object.
Specific information about the facilities offered by the Gnu software used by ReadLineBuf
is provided in the GNU Readline Library documentation
(http://cnswww.cns.cwru.edu/php/chet/readline/rltop.html).
Gnu’s readline function reads its information from the standard input file. Programs using
ReadLineBuf should normally not extract information from std::cin. However, as the
standard input file has a file descriptor (0), redirection should be possible (e.g., using
FBB::Redirector).
When the command line is kept, history expansion is offered as an option. History
expansion introduces words from the history list into the input stream, making it easy to
repeat commands, to insert elements of a previous input line into the current input line,
or to fix errors in previous command lines.
History expansion is usually performed immediately after a complete line is read.
The line selected from the history is called the event, and the portions of that line that
are processed are called words. Various modifiers are available to manipulate selected
words. This is comparable to the way a program like bash(1) breaks up its input line into
`words’.
History expansion is introduced by the use of the history expansion character, by default
equal to the !-character. Only backslash (\) and single quotes can change the history
expansion character into a normal character.
The remainder of this section is copied almost verbatim from the history(3) man-page. The
reader is referred to that man-page or to the Gnu History Library documentation for
further details.
The following event designators are supported:
o !: starts a history substitution, except when followed by a blank, newline, = or
(.
o !n: refers to command line n.
o !-n: refers to the current command line minus n.
o !! refers to the previous command. This is a synonym for `!-1’.
o !string refers to the most recent command starting with string.
o !?string[?] refers to the most recent command containing string. The trailing ?
may be omitted if string is followed immediately by a newline.
o ^string1^string2^ (quick substitution) repeats the last command, replacing string1
with string2. Equivalent to !!:s/string1/string2/.
o !# the entire command line typed so far.
Word Designators
Word designators are used to select desired words from the event. A : separates the event
specification from the word designator. It may be omitted if the word designator begins
with a ^, $, *, -, or %. Words are numbered from the beginning of the line, with the
first word being denoted by 0 (zero). Words are inserted into the current line separated
by single spaces.
o 0 (zero) The zeroth word. For the shell, this is the command word.
o n The nth word.
o ^ The first argument. That is, word 1.
o $ The last argument.
o % The word matched by the most recent ?string? search.
o x-y A range of words; `-y’ abbreviates `0-y’.
o * All of the words but the zeroth. This is a synonym for 1-$. It is not an
error to use * if there is just one word in the event; the empty string is returned
in that case.
o x* Abbreviates x-$.
o x- Abbreviates x-$ like x*, but omits the last word. If a word designator
is supplied without an event specification, the previous command is used as the
event.
Modifiers
After the optional word designator, there may appear a sequence of one or more of the
following modifiers, each preceded by a :.
o h removes a trailing file name component, leaving only the head.
o t removes all leading file name components, leaving the tail.
o r removes a trailing suffix of the form .xxx, leaving the basename.
o e removes all but the trailing suffix.
o p prints the new command but does not execute it.
o q quotes the substituted words, escaping further substitutions.
o x quotes the substituted words as with q, but break into words at blanks and
newlines.
o s/old/new/ substitutes new for the first occurrence of old in the event line. Any
delimiter can be used in place of /. The final delimiter is optional if it is the
last character of the event line. The delimiter may be quoted in old and new with
a single backslash. If & appears in new, it is replaced by old. A single
backslash will quote the &. If old is null, it is set to the last old substituted,
or, if no previous history substitutions took place, the last string in a
!?string[?] search.
o & repeats the previous substitution.
o g Causes changes to be applied over the entire event line. This is used in
conjunction with :s (e.g., :gs/old/new/) or :&. If used with :s, any delimiter can
be used in place of /, and the final delimiter is optional if it is the last
character of the event line. An a may be used as a synonym for g.
o G Apply the following s modifier once to each word in the event line.
NAMESPACE
FBB
All constructors, members, operators and manipulators, mentioned in this man-page, are
defined in the namespace FBB.
INHERITS FROM
std::streambuf
ENUMERATIONS
The enum Type defines the following value:
o DONT_EXPAND_HISTORY: history expansion is not requested;
o EXPAND_HISTORY: history expansion is requested.
The enum Expansion provides meaningful return values for the history expansion process.
Its values are:
o DONT_EXEC: history expansion succeeded, but the expanded line should not be
executed. E.g., after entering the line
ls *
the line
!!:p
should cause the using program to display, rather than exectute ls *. Note that
interpretation of this expansion return value is not the task of the ReadLineBuf
object, but of the program using the ReadLineBuf object.
o ERROR: the history expansion failed. See also the member expansionError below;
o EXPANDED: the history expansion succeeded;
o NO_EXPANSION: no history expansion took place.
STATIC MEMBERS
o ReadLineBuf &initialize(std::string const &prompt = "", Type type = NO_EXPANSION):
This static member returns the ReadLineBuf using an initial prompt, using a history
of at most std::numeric_limits<int>::max() lines, and by default not using history
expansion. If the object has already been initialized a logic_error exception is
thrown.
o ReadLineBuf &initialize(std::string const &prompt, size_t historySize, Type type =
NO_EXPANSION):
This static member initializes the ReadLineBuf using an initial prompt, an initial
history of a predefined maximum size, and by default not using history expansion.
Specifying a history size 0 results in no history being kept, any value equal to or
exceeding the predefined constant std::numeric_limits<int>::max() results in a
history of at most std::numeric_limits<int>::max() lines. If no history is
requested but type is specified as EXPAND_HISTORY a logic_error exception is
thrown. A logic_error is also thrown if the object has already been initialized.
o ReadLineBuf &instance():
This static member returns the already initialized ReadLineBuf object. If the
object has not yet been initialized a logic_error exception is thrown.
CONSTRUCTORS
As the class ReadLineBuf is a singleton class it offers no public constructors, nor are
overloaded assignment operators available.
MEMBER FUNCTIONS
All members of std::streambuf are available, as FBB::ReadLineBuf inherits from this class.
o ReadLineBuf::Expansion expansion() const:
The status of the history expansion after retrieving a line from the terminal is
returned. Its value is determined after each line retrieved from the terminal. If
no history expansion is requested it returns Expansion::ERROR.
o std::string const &expansionError() const:
A short textual description of the nature of the error when expansion returns
Expansion::ERROR is returned. If no history expansion is requested an empty string
is returned.
o bool setExpansion(Type type):
History expansion can be activated or stopped using this member. When history
expansion is requested but the ReadLineBuf object maintains no history the function
returns false. Otherwise it returns true.
o void setPrompt(std::string const &prompt = ""):
The prompt that is displayed in front of the next line read from the terminal can
be modified by this member. When called without arguments no prompt will be
displayed. setPrompt can be called while input lines are being received. The new
prompt will be active after the current line has been read from the terminal.
o bool useTimestamps(std::string (*timestamp)() = 0):
When initialized with the address of a function returning a std::string the entered
commands will be given a timestamp equal to the text returned by the function
pointed to by timestamp. The timestamps can be retrieved using the
ReadLineHistory(3) object. By default or after passing an explicit 0-pointer to
useTimestamps no timestamps are stored. The value false is returned when no
history is kept, otherwise true is returned.
EXAMPLE
#include <iostream>
#include <istream>
#include <cstdio>
#include <sstream>
#include <iomanip>
#include <bobcat/readlinebuf>
//#include "../readlinebuf"
using namespace std;
using namespace FBB;
int main()
{
ReadLineBuf &readlineBuf =
ReadLineBuf::initialize("", 10, ReadLineBuf::EXPAND_HISTORY);
istream in(&readlineBuf);
size_t count = 0;
string line;
while (true)
{
ostringstream prompt;
prompt << setw(2) << ++count << ": ";
readlineBuf.setPrompt(prompt.str());
if (!getline(in, line)) // uses the last-set prompt
break;
cout << "Retrieved: " << line << "\n"
"Expansion status: ";
switch (readlineBuf.expansion())
{
case ReadLineBuf::ERROR:
cout << "ERROR: " << readlineBuf.expansionError() << ’\n’;
break;
case ReadLineBuf::NO_EXPANSION:
cout << "no expansion performed\n";
break;
case ReadLineBuf::DONT_EXEC:
cout << "don’t execute the expanded line\n";
break;
case ReadLineBuf::EXPANDED:
cout << "expansion successfully performed\n";
break;
}
}
}
FILES
bobcat/readlinebuf - defines the class interface
SEE ALSO
bobcat(7), readline(3), readlinehistory(3), readlinestream(3)
BUGS
None Reported.
BOBCAT PROJECT FILES
o https://fbb-git.gitlab.io/bobcat/: gitlab project page;
o bobcat_6.02.02-x.dsc: detached signature;
o bobcat_6.02.02-x.tar.gz: source archive;
o bobcat_6.02.02-x_i386.changes: change log;
o libbobcat1_6.02.02-x_*.deb: debian package containing the libraries;
o libbobcat1-dev_6.02.02-x_*.deb: debian package containing the libraries, headers
and manual pages;
BOBCAT
Bobcat is an acronym of `Brokken’s Own Base Classes And Templates’.
COPYRIGHT
This is free software, distributed under the terms of the GNU General Public License
(GPL).
AUTHOR
Frank B. Brokken (f.b.brokken@rug.nl).