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diff --git a/doc/hstech.texi b/doc/hstech.texi new file mode 100644 index 0000000..47ba8a5 --- /dev/null +++ b/doc/hstech.texi @@ -0,0 +1,573 @@ +@ignore +This file documents the user interface to the GNU History library. + +Copyright (C) 1988-2006 Free Software Foundation, Inc. +Authored by Brian Fox and Chet Ramey. + +Permission is granted to make and distribute verbatim copies of this manual +provided the copyright notice and this permission notice are preserved on +all copies. + +Permission is granted to process this file through Tex and print the +results, provided the printed document carries copying permission notice +identical to this one except for the removal of this paragraph (this +paragraph not being relevant to the printed manual). + +Permission is granted to copy and distribute modified versions of this +manual under the conditions for verbatim copying, provided also that the +GNU Copyright statement is available to the distributee, and provided that +the entire resulting derived work is distributed under the terms of a +permission notice identical to this one. + +Permission is granted to copy and distribute translations of this manual +into another language, under the above conditions for modified versions. +@end ignore + +@node Programming with GNU History +@chapter Programming with GNU History + +This chapter describes how to interface programs that you write +with the @sc{gnu} History Library. +It should be considered a technical guide. +For information on the interactive use of @sc{gnu} History, @pxref{Using +History Interactively}. + +@menu +* Introduction to History:: What is the GNU History library for? +* History Storage:: How information is stored. +* History Functions:: Functions that you can use. +* History Variables:: Variables that control behaviour. +* History Programming Example:: Example of using the GNU History Library. +@end menu + +@node Introduction to History +@section Introduction to History + +Many programs read input from the user a line at a time. The @sc{gnu} +History library is able to keep track of those lines, associate arbitrary +data with each line, and utilize information from previous lines in +composing new ones. + +The programmer using the History library has available functions +for remembering lines on a history list, associating arbitrary data +with a line, removing lines from the list, searching through the list +for a line containing an arbitrary text string, and referencing any line +in the list directly. In addition, a history @dfn{expansion} function +is available which provides for a consistent user interface across +different programs. + +The user using programs written with the History library has the +benefit of a consistent user interface with a set of well-known +commands for manipulating the text of previous lines and using that text +in new commands. The basic history manipulation commands are similar to +the history substitution provided by @code{csh}. + +If the programmer desires, he can use the Readline library, which +includes some history manipulation by default, and has the added +advantage of command line editing. + +Before declaring any functions using any functionality the History +library provides in other code, an application writer should include +the file @code{<readline/history.h>} in any file that uses the +History library's features. It supplies extern declarations for all +of the library's public functions and variables, and declares all of +the public data structures. + +@node History Storage +@section History Storage + +The history list is an array of history entries. A history entry is +declared as follows: + +@example +typedef void *histdata_t; + +typedef struct _hist_entry @{ + char *line; + char *timestamp; + histdata_t data; +@} HIST_ENTRY; +@end example + +The history list itself might therefore be declared as + +@example +HIST_ENTRY **the_history_list; +@end example + +The state of the History library is encapsulated into a single structure: + +@example +/* + * A structure used to pass around the current state of the history. + */ +typedef struct _hist_state @{ + HIST_ENTRY **entries; /* Pointer to the entries themselves. */ + int offset; /* The location pointer within this array. */ + int length; /* Number of elements within this array. */ + int size; /* Number of slots allocated to this array. */ + int flags; +@} HISTORY_STATE; +@end example + +If the flags member includes @code{HS_STIFLED}, the history has been +stifled. + +@node History Functions +@section History Functions + +This section describes the calling sequence for the various functions +exported by the @sc{gnu} History library. + +@menu +* Initializing History and State Management:: Functions to call when you + want to use history in a + program. +* History List Management:: Functions used to manage the list + of history entries. +* Information About the History List:: Functions returning information about + the history list. +* Moving Around the History List:: Functions used to change the position + in the history list. +* Searching the History List:: Functions to search the history list + for entries containing a string. +* Managing the History File:: Functions that read and write a file + containing the history list. +* History Expansion:: Functions to perform csh-like history + expansion. +@end menu + +@node Initializing History and State Management +@subsection Initializing History and State Management + +This section describes functions used to initialize and manage +the state of the History library when you want to use the history +functions in your program. + +@deftypefun void using_history (void) +Begin a session in which the history functions might be used. This +initializes the interactive variables. +@end deftypefun + +@deftypefun {HISTORY_STATE *} history_get_history_state (void) +Return a structure describing the current state of the input history. +@end deftypefun + +@deftypefun void history_set_history_state (HISTORY_STATE *state) +Set the state of the history list according to @var{state}. +@end deftypefun + +@node History List Management +@subsection History List Management + +These functions manage individual entries on the history list, or set +parameters managing the list itself. + +@deftypefun void add_history (const char *string) +Place @var{string} at the end of the history list. The associated data +field (if any) is set to @code{NULL}. +@end deftypefun + +@deftypefun void add_history_time (const char *string) +Change the time stamp associated with the most recent history entry to +@var{string}. +@end deftypefun + +@deftypefun {HIST_ENTRY *} remove_history (int which) +Remove history entry at offset @var{which} from the history. The +removed element is returned so you can free the line, data, +and containing structure. +@end deftypefun + +@deftypefun {histdata_t} free_history_entry (HIST_ENTRY *histent) +Free the history entry @var{histent} and any history library private +data associated with it. Returns the application-specific data +so the caller can dispose of it. +@end deftypefun + +@deftypefun {HIST_ENTRY *} replace_history_entry (int which, const char *line, histdata_t data) +Make the history entry at offset @var{which} have @var{line} and @var{data}. +This returns the old entry so the caller can dispose of any +application-specific data. In the case +of an invalid @var{which}, a @code{NULL} pointer is returned. +@end deftypefun + +@deftypefun void clear_history (void) +Clear the history list by deleting all the entries. +@end deftypefun + +@deftypefun void stifle_history (int max) +Stifle the history list, remembering only the last @var{max} entries. +@end deftypefun + +@deftypefun int unstifle_history (void) +Stop stifling the history. This returns the previously-set +maximum number of history entries (as set by @code{stifle_history()}). +The value is positive if the history was +stifled, negative if it wasn't. +@end deftypefun + +@deftypefun int history_is_stifled (void) +Returns non-zero if the history is stifled, zero if it is not. +@end deftypefun + +@node Information About the History List +@subsection Information About the History List + +These functions return information about the entire history list or +individual list entries. + +@deftypefun {HIST_ENTRY **} history_list (void) +Return a @code{NULL} terminated array of @code{HIST_ENTRY *} which is the +current input history. Element 0 of this list is the beginning of time. +If there is no history, return @code{NULL}. +@end deftypefun + +@deftypefun int where_history (void) +Returns the offset of the current history element. +@end deftypefun + +@deftypefun {HIST_ENTRY *} current_history (void) +Return the history entry at the current position, as determined by +@code{where_history()}. If there is no entry there, return a @code{NULL} +pointer. +@end deftypefun + +@deftypefun {HIST_ENTRY *} history_get (int offset) +Return the history entry at position @var{offset}, starting from +@code{history_base} (@pxref{History Variables}). +If there is no entry there, or if @var{offset} +is greater than the history length, return a @code{NULL} pointer. +@end deftypefun + +@deftypefun time_t history_get_time (HIST_ENTRY *entry) +Return the time stamp associated with the history entry @var{entry}. +@end deftypefun + +@deftypefun int history_total_bytes (void) +Return the number of bytes that the primary history entries are using. +This function returns the sum of the lengths of all the lines in the +history. +@end deftypefun + +@node Moving Around the History List +@subsection Moving Around the History List + +These functions allow the current index into the history list to be +set or changed. + +@deftypefun int history_set_pos (int pos) +Set the current history offset to @var{pos}, an absolute index +into the list. +Returns 1 on success, 0 if @var{pos} is less than zero or greater +than the number of history entries. +@end deftypefun + +@deftypefun {HIST_ENTRY *} previous_history (void) +Back up the current history offset to the previous history entry, and +return a pointer to that entry. If there is no previous entry, return +a @code{NULL} pointer. +@end deftypefun + +@deftypefun {HIST_ENTRY *} next_history (void) +Move the current history offset forward to the next history entry, and +return the a pointer to that entry. If there is no next entry, return +a @code{NULL} pointer. +@end deftypefun + +@node Searching the History List +@subsection Searching the History List +@cindex History Searching + +These functions allow searching of the history list for entries containing +a specific string. Searching may be performed both forward and backward +from the current history position. The search may be @dfn{anchored}, +meaning that the string must match at the beginning of the history entry. +@cindex anchored search + +@deftypefun int history_search (const char *string, int direction) +Search the history for @var{string}, starting at the current history offset. +If @var{direction} is less than 0, then the search is through +previous entries, otherwise through subsequent entries. +If @var{string} is found, then +the current history index is set to that history entry, and the value +returned is the offset in the line of the entry where +@var{string} was found. Otherwise, nothing is changed, and a -1 is +returned. +@end deftypefun + +@deftypefun int history_search_prefix (const char *string, int direction) +Search the history for @var{string}, starting at the current history +offset. The search is anchored: matching lines must begin with +@var{string}. If @var{direction} is less than 0, then the search is +through previous entries, otherwise through subsequent entries. +If @var{string} is found, then the +current history index is set to that entry, and the return value is 0. +Otherwise, nothing is changed, and a -1 is returned. +@end deftypefun + +@deftypefun int history_search_pos (const char *string, int direction, int pos) +Search for @var{string} in the history list, starting at @var{pos}, an +absolute index into the list. If @var{direction} is negative, the search +proceeds backward from @var{pos}, otherwise forward. Returns the absolute +index of the history element where @var{string} was found, or -1 otherwise. +@end deftypefun + +@node Managing the History File +@subsection Managing the History File + +The History library can read the history from and write it to a file. +This section documents the functions for managing a history file. + +@deftypefun int read_history (const char *filename) +Add the contents of @var{filename} to the history list, a line at a time. +If @var{filename} is @code{NULL}, then read from @file{~/.history}. +Returns 0 if successful, or @code{errno} if not. +@end deftypefun + +@deftypefun int read_history_range (const char *filename, int from, int to) +Read a range of lines from @var{filename}, adding them to the history list. +Start reading at line @var{from} and end at @var{to}. +If @var{from} is zero, start at the beginning. If @var{to} is less than +@var{from}, then read until the end of the file. If @var{filename} is +@code{NULL}, then read from @file{~/.history}. Returns 0 if successful, +or @code{errno} if not. +@end deftypefun + +@deftypefun int write_history (const char *filename) +Write the current history to @var{filename}, overwriting @var{filename} +if necessary. +If @var{filename} is @code{NULL}, then write the history list to +@file{~/.history}. +Returns 0 on success, or @code{errno} on a read or write error. +@end deftypefun + +@deftypefun int append_history (int nelements, const char *filename) +Append the last @var{nelements} of the history list to @var{filename}. +If @var{filename} is @code{NULL}, then append to @file{~/.history}. +Returns 0 on success, or @code{errno} on a read or write error. +@end deftypefun + +@deftypefun int history_truncate_file (const char *filename, int nlines) +Truncate the history file @var{filename}, leaving only the last +@var{nlines} lines. +If @var{filename} is @code{NULL}, then @file{~/.history} is truncated. +Returns 0 on success, or @code{errno} on failure. +@end deftypefun + +@node History Expansion +@subsection History Expansion + +These functions implement history expansion. + +@deftypefun int history_expand (char *string, char **output) +Expand @var{string}, placing the result into @var{output}, a pointer +to a string (@pxref{History Interaction}). Returns: +@table @code +@item 0 +If no expansions took place (or, if the only change in +the text was the removal of escape characters preceding the history expansion +character); +@item 1 +if expansions did take place; +@item -1 +if there was an error in expansion; +@item 2 +if the returned line should be displayed, but not executed, +as with the @code{:p} modifier (@pxref{Modifiers}). +@end table + +If an error ocurred in expansion, then @var{output} contains a descriptive +error message. +@end deftypefun + +@deftypefun {char *} get_history_event (const char *string, int *cindex, int qchar) +Returns the text of the history event beginning at @var{string} + +@var{*cindex}. @var{*cindex} is modified to point to after the event +specifier. At function entry, @var{cindex} points to the index into +@var{string} where the history event specification begins. @var{qchar} +is a character that is allowed to end the event specification in addition +to the ``normal'' terminating characters. +@end deftypefun + +@deftypefun {char **} history_tokenize (const char *string) +Return an array of tokens parsed out of @var{string}, much as the +shell might. The tokens are split on the characters in the +@var{history_word_delimiters} variable, +and shell quoting conventions are obeyed. +@end deftypefun + +@deftypefun {char *} history_arg_extract (int first, int last, const char *string) +Extract a string segment consisting of the @var{first} through @var{last} +arguments present in @var{string}. Arguments are split using +@code{history_tokenize}. +@end deftypefun + +@node History Variables +@section History Variables + +This section describes the externally-visible variables exported by +the @sc{gnu} History Library. + +@deftypevar int history_base +The logical offset of the first entry in the history list. +@end deftypevar + +@deftypevar int history_length +The number of entries currently stored in the history list. +@end deftypevar + +@deftypevar int history_max_entries +The maximum number of history entries. This must be changed using +@code{stifle_history()}. +@end deftypevar + +@deftypevar int history_write_timestamps +If non-zero, timestamps are written to the history file, so they can be +preserved between sessions. The default value is 0, meaning that +timestamps are not saved. +@end deftypevar + +@deftypevar char history_expansion_char +The character that introduces a history event. The default is @samp{!}. +Setting this to 0 inhibits history expansion. +@end deftypevar + +@deftypevar char history_subst_char +The character that invokes word substitution if found at the start of +a line. The default is @samp{^}. +@end deftypevar + +@deftypevar char history_comment_char +During tokenization, if this character is seen as the first character +of a word, then it and all subsequent characters up to a newline are +ignored, suppressing history expansion for the remainder of the line. +This is disabled by default. +@end deftypevar + +@deftypevar {char *} history_word_delimiters +The characters that separate tokens for @code{history_tokenize()}. +The default value is @code{" \t\n()<>;&|"}. +@end deftypevar + +@deftypevar {char *} history_search_delimiter_chars +The list of additional characters which can delimit a history search +string, in addition to space, TAB, @samp{:} and @samp{?} in the case of +a substring search. The default is empty. +@end deftypevar + +@deftypevar {char *} history_no_expand_chars +The list of characters which inhibit history expansion if found immediately +following @var{history_expansion_char}. The default is space, tab, newline, +carriage return, and @samp{=}. +@end deftypevar + +@deftypevar int history_quotes_inhibit_expansion +If non-zero, single-quoted words are not scanned for the history expansion +character. The default value is 0. +@end deftypevar + +@deftypevar {rl_linebuf_func_t *} history_inhibit_expansion_function +This should be set to the address of a function that takes two arguments: +a @code{char *} (@var{string}) +and an @code{int} index into that string (@var{i}). +It should return a non-zero value if the history expansion starting at +@var{string[i]} should not be performed; zero if the expansion should +be done. +It is intended for use by applications like Bash that use the history +expansion character for additional purposes. +By default, this variable is set to @code{NULL}. +@end deftypevar + +@node History Programming Example +@section History Programming Example + +The following program demonstrates simple use of the @sc{gnu} History Library. + +@smallexample +#include <stdio.h> +#include <readline/history.h> + +main (argc, argv) + int argc; + char **argv; +@{ + char line[1024], *t; + int len, done = 0; + + line[0] = 0; + + using_history (); + while (!done) + @{ + printf ("history$ "); + fflush (stdout); + t = fgets (line, sizeof (line) - 1, stdin); + if (t && *t) + @{ + len = strlen (t); + if (t[len - 1] == '\n') + t[len - 1] = '\0'; + @} + + if (!t) + strcpy (line, "quit"); + + if (line[0]) + @{ + char *expansion; + int result; + + result = history_expand (line, &expansion); + if (result) + fprintf (stderr, "%s\n", expansion); + + if (result < 0 || result == 2) + @{ + free (expansion); + continue; + @} + + add_history (expansion); + strncpy (line, expansion, sizeof (line) - 1); + free (expansion); + @} + + if (strcmp (line, "quit") == 0) + done = 1; + else if (strcmp (line, "save") == 0) + write_history ("history_file"); + else if (strcmp (line, "read") == 0) + read_history ("history_file"); + else if (strcmp (line, "list") == 0) + @{ + register HIST_ENTRY **the_list; + register int i; + + the_list = history_list (); + if (the_list) + for (i = 0; the_list[i]; i++) + printf ("%d: %s\n", i + history_base, the_list[i]->line); + @} + else if (strncmp (line, "delete", 6) == 0) + @{ + int which; + if ((sscanf (line + 6, "%d", &which)) == 1) + @{ + HIST_ENTRY *entry = remove_history (which); + if (!entry) + fprintf (stderr, "No such entry %d\n", which); + else + @{ + free (entry->line); + free (entry); + @} + @} + else + @{ + fprintf (stderr, "non-numeric arg given to `delete'\n"); + @} + @} + @} +@} +@end smallexample |