312 lines
10 KiB
Plaintext
312 lines
10 KiB
Plaintext
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@ignore
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This file documents the user interface to the GNU History library.
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Copyright (C) 1988, 1991 Free Software Foundation, Inc.
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Authored by Brian Fox.
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Permission is granted to make and distribute verbatim copies of this manual
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provided the copyright notice and this permission notice are preserved on
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all copies.
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Permission is granted to process this file through Tex and print the
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results, provided the printed document carries copying permission notice
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identical to this one except for the removal of this paragraph (this
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paragraph not being relevant to the printed manual).
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Permission is granted to copy and distribute modified versions of this
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manual under the conditions for verbatim copying, provided also that the
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GNU Copyright statement is available to the distributee, and provided that
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the entire resulting derived work is distributed under the terms of a
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permission notice identical to this one.
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Permission is granted to copy and distribute translations of this manual
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into another language, under the above conditions for modified versions.
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@end ignore
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@node Programming with GNU History
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@chapter Programming with GNU History
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This chapter describes how to interface the GNU History Library with
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programs that you write. It should be considered a technical guide.
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For information on the interactive use of GNU History, @pxref{Using
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History Interactively}.
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@menu
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* Introduction to History:: What is the GNU History library for?
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* History Storage:: How information is stored.
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* History Functions:: Functions that you can use.
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* History Variables:: Variables that control behaviour.
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* History Programming Example:: Example of using the GNU History Library.
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@end menu
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@node Introduction to History
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@section Introduction to History
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Many programs read input from the user a line at a time. The GNU history
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library is able to keep track of those lines, associate arbitrary data with
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each line, and utilize information from previous lines in making up new
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ones.
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The programmer using the History library has available to him functions
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for remembering lines on a history stack, associating arbitrary data
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with a line, removing lines from the stack, searching through the stack
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for a line containing an arbitrary text string, and referencing any line
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on the stack directly. In addition, a history @dfn{expansion} function
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is available which provides for a consistent user interface across many
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different programs.
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The end-user using programs written with the History library has the
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benifit of a consistent user interface, with a set of well-known
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commands for manipulating the text of previous lines and using that text
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in new commands. The basic history manipulation commands are similar to
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the history substitution used by @code{Csh}.
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If the programmer desires, he can use the Readline library, which
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includes some history manipulation by default, and has the added
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advantage of Emacs style command line editing.
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@node History Storage
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@section History Storage
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@example
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typedef struct _hist_entry @{
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char *line;
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char *data;
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@} HIST_ENTRY;
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@end example
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@node History Functions
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@section History Functions
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This section describes the calling sequence for the various functions
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present in GNU History.
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@defun {void using_history} ()
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Begin a session in which the history functions might be used. This
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just initializes the interactive variables.
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@end defun
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@defun {void add_history} (char *string)
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Place @var{string} at the end of the history list. The associated data
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field (if any) is set to @code{NULL}.
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@end defun
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@defun {int where_history} ()
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Returns the number which says what history element we are now looking
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at.
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@end defun
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@defun {int history_set_pos} (int pos)
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Set the position in the history list to @var{pos}.
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@end defun
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@defun {int history_search_pos} (char *string, int direction, int pos)
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Search for @var{string} in the history list, starting at @var{pos}, an
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absolute index into the list. @var{direction}, if negative, says to search
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backwards from @var{pos}, else forwards. Returns the absolute index of
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the history element where @var{string} was found, or -1 otherwise.
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@end defun
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@defun {HIST_ENTRY *remove_history} ();
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Remove history element @var{which} from the history. The removed
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element is returned to you so you can free the line, data,
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and containing structure.
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@end defun
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@defun {void stifle_history} (int max)
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Stifle the history list, remembering only @var{max} number of entries.
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@end defun
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@defun {int unstifle_history} ();
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Stop stifling the history. This returns the previous amount the
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history was stifled by. The value is positive if the history was
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stifled, negative if it wasn't.
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@end defun
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@defun {int read_history} (char *filename)
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Add the contents of @var{filename} to the history list, a line at a
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time. If @var{filename} is @code{NULL}, then read from
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@file{~/.history}. Returns 0 if successful, or errno if not.
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@end defun
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@defun {int read_history_range} (char *filename, int from, int to)
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Read a range of lines from @var{filename}, adding them to the history list.
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Start reading at the @var{from}'th line and end at the @var{to}'th. If
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@var{from} is zero, start at the beginning. If @var{to} is less than
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@var{from}, then read until the end of the file. If @var{filename} is
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@code{NULL}, then read from @file{~/.history}. Returns 0 if successful,
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or @code{errno} if not.
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@end defun
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@defun {int write_history} (char *filename)
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Append the current history to @var{filename}. If @var{filename} is
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@code{NULL}, then append the history list to @file{~/.history}. Values
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returned are as in @code{read_history ()}.
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@end defun
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@defun {int append_history} (int nelements, char *filename)
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Append @var{nelement} entries to @var{filename}. The entries appended
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are from the end of the list minus @var{nelements} up to the end of the
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list.
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@end defun
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@defun {HIST_ENTRY *replace_history_entry} ()
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Make the history entry at @var{which} have @var{line} and @var{data}.
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This returns the old entry so you can dispose of the data. In the case
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of an invalid @var{which}, a @code{NULL} pointer is returned.
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@end defun
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@defun {HIST_ENTRY *current_history} ()
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Return the history entry at the current position, as determined by
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@code{history_offset}. If there is no entry there, return a @code{NULL}
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pointer.
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@end defun
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@defun {HIST_ENTRY *previous_history} ()
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Back up @var{history_offset} to the previous history entry, and return a
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pointer to that entry. If there is no previous entry, return a
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@code{NULL} pointer.
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@end defun
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@defun {HIST_ENTRY *next_history} ()
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Move @code{history_offset} forward to the next history entry, and return
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the a pointer to that entry. If there is no next entry, return a
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@code{NULL} pointer.
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@end defun
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@defun {HIST_ENTRY **history_list} ()
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Return a @code{NULL} terminated array of @code{HIST_ENTRY} which is the
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current input history. Element 0 of this list is the beginning of time.
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If there is no history, return @code{NULL}.
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@end defun
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@defun {int history_search} (char *string, int direction)
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Search the history for @var{string}, starting at @code{history_offset}.
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If @var{direction} < 0, then the search is through previous entries,
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else through subsequent. If @var{string} is found, then
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@code{current_history ()} is the history entry, and the value of this
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function is the offset in the line of that history entry that the
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@var{string} was found in. Otherwise, nothing is changed, and a -1 is
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returned.
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@end defun
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@defun {int history_expand} (char *string, char **output)
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Expand @var{string}, placing the result into @var{output}, a pointer
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to a string. Returns:
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@table @code
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@item 0
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If no expansions took place (or, if the only change in
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the text was the de-slashifying of the history expansion
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character),
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@item 1
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if expansions did take place, or
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@item -1
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if there was an error in expansion.
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@end table
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If an error ocurred in expansion, then @var{output} contains a descriptive
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error message.
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@end defun
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@defun {char *history_arg_extract} (int first, int last, char *string)
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Extract a string segment consisting of the @var{first} through @var{last}
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arguments present in @var{string}. Arguments are broken up as in
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the GNU Bash shell.
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@end defun
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@defun {int history_total_bytes} ();
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Return the number of bytes that the primary history entries are using.
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This just adds up the lengths of @code{the_history->lines}.
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@end defun
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@node History Variables
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@section History Variables
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This section describes the variables in GNU History that are externally
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visible.
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@defvar {int history_base}
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For convenience only. You set this when interpreting history commands.
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It is the logical offset of the first history element.
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@end defvar
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@node History Programming Example
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@section History Programming Example
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The following snippet of code demonstrates simple use of the GNU History
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Library.
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@smallexample
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main ()
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@{
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char line[1024], *t;
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int done = 0;
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line[0] = 0;
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while (!done)
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@{
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fprintf (stdout, "history%% ");
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t = gets (line);
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if (!t)
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strcpy (line, "quit");
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if (line[0])
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@{
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char *expansion;
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int result;
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using_history ();
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result = history_expand (line, &expansion);
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strcpy (line, expansion);
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free (expansion);
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if (result)
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fprintf (stderr, "%s\n", line);
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if (result < 0)
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continue;
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add_history (line);
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@}
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if (strcmp (line, "quit") == 0) done = 1;
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if (strcmp (line, "save") == 0) write_history (0);
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if (strcmp (line, "read") == 0) read_history (0);
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if (strcmp (line, "list") == 0)
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@{
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register HIST_ENTRY **the_list = history_list ();
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register int i;
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if (the_list)
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for (i = 0; the_list[i]; i++)
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fprintf (stdout, "%d: %s\n",
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i + history_base, the_list[i]->line);
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@}
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if (strncmp (line, "delete", strlen ("delete")) == 0)
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@{
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int which;
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if ((sscanf (line + strlen ("delete"), "%d", &which)) == 1)
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@{
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HIST_ENTRY *entry = remove_history (which);
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if (!entry)
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fprintf (stderr, "No such entry %d\n", which);
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else
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@{
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free (entry->line);
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free (entry);
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@}
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@}
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else
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@{
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fprintf (stderr, "non-numeric arg given to `delete'\n");
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@}
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@}
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@}
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@}
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@end smallexample
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