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1 | @ignore |
2 | This file documents the user interface to the GNU History library. | |
3 | ||
4 | Copyright (C) 1988-2002 Free Software Foundation, Inc. | |
5 | Authored by Brian Fox and Chet Ramey. | |
6 | ||
7 | Permission is granted to make and distribute verbatim copies of this manual | |
8 | provided the copyright notice and this permission notice are preserved on | |
9 | all copies. | |
10 | ||
11 | Permission is granted to process this file through Tex and print the | |
12 | results, provided the printed document carries copying permission notice | |
13 | identical to this one except for the removal of this paragraph (this | |
14 | paragraph not being relevant to the printed manual). | |
15 | ||
16 | Permission is granted to copy and distribute modified versions of this | |
17 | manual under the conditions for verbatim copying, provided also that the | |
18 | GNU Copyright statement is available to the distributee, and provided that | |
19 | the entire resulting derived work is distributed under the terms of a | |
20 | permission notice identical to this one. | |
21 | ||
22 | Permission is granted to copy and distribute translations of this manual | |
23 | into another language, under the above conditions for modified versions. | |
24 | @end ignore | |
25 | ||
26 | @node Programming with GNU History | |
27 | @chapter Programming with GNU History | |
28 | ||
29 | This chapter describes how to interface programs that you write | |
30 | with the @sc{gnu} History Library. | |
31 | It should be considered a technical guide. | |
32 | For information on the interactive use of @sc{gnu} History, @pxref{Using | |
33 | History Interactively}. | |
34 | ||
35 | @menu | |
36 | * Introduction to History:: What is the GNU History library for? | |
37 | * History Storage:: How information is stored. | |
38 | * History Functions:: Functions that you can use. | |
39 | * History Variables:: Variables that control behaviour. | |
40 | * History Programming Example:: Example of using the GNU History Library. | |
41 | @end menu | |
42 | ||
43 | @node Introduction to History | |
44 | @section Introduction to History | |
45 | ||
46 | Many programs read input from the user a line at a time. The @sc{gnu} | |
47 | History library is able to keep track of those lines, associate arbitrary | |
48 | data with each line, and utilize information from previous lines in | |
49 | composing new ones. | |
50 | ||
51 | The programmer using the History library has available functions | |
52 | for remembering lines on a history list, associating arbitrary data | |
53 | with a line, removing lines from the list, searching through the list | |
54 | for a line containing an arbitrary text string, and referencing any line | |
55 | in the list directly. In addition, a history @dfn{expansion} function | |
56 | is available which provides for a consistent user interface across | |
57 | different programs. | |
58 | ||
59 | The user using programs written with the History library has the | |
60 | benefit of a consistent user interface with a set of well-known | |
61 | commands for manipulating the text of previous lines and using that text | |
62 | in new commands. The basic history manipulation commands are similar to | |
63 | the history substitution provided by @code{csh}. | |
64 | ||
65 | If the programmer desires, he can use the Readline library, which | |
66 | includes some history manipulation by default, and has the added | |
67 | advantage of command line editing. | |
68 | ||
69 | Before declaring any functions using any functionality the History | |
70 | library provides in other code, an application writer should include | |
71 | the file @code{<readline/history.h>} in any file that uses the | |
72 | History library's features. It supplies extern declarations for all | |
73 | of the library's public functions and variables, and declares all of | |
74 | the public data structures. | |
75 | ||
76 | @node History Storage | |
77 | @section History Storage | |
78 | ||
79 | The history list is an array of history entries. A history entry is | |
80 | declared as follows: | |
81 | ||
82 | @example | |
83 | typedef void *histdata_t; | |
84 | ||
85 | typedef struct _hist_entry @{ | |
86 | char *line; | |
87 | char *timestamp; | |
88 | histdata_t data; | |
89 | @} HIST_ENTRY; | |
90 | @end example | |
91 | ||
92 | The history list itself might therefore be declared as | |
93 | ||
94 | @example | |
95 | HIST_ENTRY **the_history_list; | |
96 | @end example | |
97 | ||
98 | The state of the History library is encapsulated into a single structure: | |
99 | ||
100 | @example | |
101 | /* | |
102 | * A structure used to pass around the current state of the history. | |
103 | */ | |
104 | typedef struct _hist_state @{ | |
105 | HIST_ENTRY **entries; /* Pointer to the entries themselves. */ | |
106 | int offset; /* The location pointer within this array. */ | |
107 | int length; /* Number of elements within this array. */ | |
108 | int size; /* Number of slots allocated to this array. */ | |
109 | int flags; | |
110 | @} HISTORY_STATE; | |
111 | @end example | |
112 | ||
113 | If the flags member includes @code{HS_STIFLED}, the history has been | |
114 | stifled. | |
115 | ||
116 | @node History Functions | |
117 | @section History Functions | |
118 | ||
119 | This section describes the calling sequence for the various functions | |
120 | exported by the @sc{gnu} History library. | |
121 | ||
122 | @menu | |
123 | * Initializing History and State Management:: Functions to call when you | |
124 | want to use history in a | |
125 | program. | |
126 | * History List Management:: Functions used to manage the list | |
127 | of history entries. | |
128 | * Information About the History List:: Functions returning information about | |
129 | the history list. | |
130 | * Moving Around the History List:: Functions used to change the position | |
131 | in the history list. | |
132 | * Searching the History List:: Functions to search the history list | |
133 | for entries containing a string. | |
134 | * Managing the History File:: Functions that read and write a file | |
135 | containing the history list. | |
136 | * History Expansion:: Functions to perform csh-like history | |
137 | expansion. | |
138 | @end menu | |
139 | ||
140 | @node Initializing History and State Management | |
141 | @subsection Initializing History and State Management | |
142 | ||
143 | This section describes functions used to initialize and manage | |
144 | the state of the History library when you want to use the history | |
145 | functions in your program. | |
146 | ||
147 | @deftypefun void using_history (void) | |
148 | Begin a session in which the history functions might be used. This | |
149 | initializes the interactive variables. | |
150 | @end deftypefun | |
151 | ||
152 | @deftypefun {HISTORY_STATE *} history_get_history_state (void) | |
153 | Return a structure describing the current state of the input history. | |
154 | @end deftypefun | |
155 | ||
156 | @deftypefun void history_set_history_state (HISTORY_STATE *state) | |
157 | Set the state of the history list according to @var{state}. | |
158 | @end deftypefun | |
159 | ||
160 | @node History List Management | |
161 | @subsection History List Management | |
162 | ||
163 | These functions manage individual entries on the history list, or set | |
164 | parameters managing the list itself. | |
165 | ||
166 | @deftypefun void add_history (const char *string) | |
167 | Place @var{string} at the end of the history list. The associated data | |
168 | field (if any) is set to @code{NULL}. | |
169 | @end deftypefun | |
170 | ||
171 | @deftypefun void add_history_time (const char *string) | |
172 | Change the time stamp associated with the most recent history entry to | |
173 | @var{string}. | |
174 | @end deftypefun | |
175 | ||
176 | @deftypefun {HIST_ENTRY *} remove_history (int which) | |
177 | Remove history entry at offset @var{which} from the history. The | |
178 | removed element is returned so you can free the line, data, | |
179 | and containing structure. | |
180 | @end deftypefun | |
181 | ||
182 | @deftypefun {histdata_t} free_history_entry (HIST_ENTRY *histent) | |
183 | Free the history entry @var{histent} and any history library private | |
184 | data associated with it. Returns the application-specific data | |
185 | so the caller can dispose of it. | |
186 | @end deftypefun | |
187 | ||
188 | @deftypefun {HIST_ENTRY *} replace_history_entry (int which, const char *line, histdata_t data) | |
189 | Make the history entry at offset @var{which} have @var{line} and @var{data}. | |
190 | This returns the old entry so the caller can dispose of any | |
191 | application-specific data. In the case | |
192 | of an invalid @var{which}, a @code{NULL} pointer is returned. | |
193 | @end deftypefun | |
194 | ||
195 | @deftypefun void clear_history (void) | |
196 | Clear the history list by deleting all the entries. | |
197 | @end deftypefun | |
198 | ||
199 | @deftypefun void stifle_history (int max) | |
200 | Stifle the history list, remembering only the last @var{max} entries. | |
201 | @end deftypefun | |
202 | ||
203 | @deftypefun int unstifle_history (void) | |
204 | Stop stifling the history. This returns the previously-set | |
205 | maximum number of history entries (as set by @code{stifle_history()}). | |
206 | The value is positive if the history was | |
207 | stifled, negative if it wasn't. | |
208 | @end deftypefun | |
209 | ||
210 | @deftypefun int history_is_stifled (void) | |
211 | Returns non-zero if the history is stifled, zero if it is not. | |
212 | @end deftypefun | |
213 | ||
214 | @node Information About the History List | |
215 | @subsection Information About the History List | |
216 | ||
217 | These functions return information about the entire history list or | |
218 | individual list entries. | |
219 | ||
220 | @deftypefun {HIST_ENTRY **} history_list (void) | |
221 | Return a @code{NULL} terminated array of @code{HIST_ENTRY *} which is the | |
222 | current input history. Element 0 of this list is the beginning of time. | |
223 | If there is no history, return @code{NULL}. | |
224 | @end deftypefun | |
225 | ||
226 | @deftypefun int where_history (void) | |
227 | Returns the offset of the current history element. | |
228 | @end deftypefun | |
229 | ||
230 | @deftypefun {HIST_ENTRY *} current_history (void) | |
231 | Return the history entry at the current position, as determined by | |
232 | @code{where_history()}. If there is no entry there, return a @code{NULL} | |
233 | pointer. | |
234 | @end deftypefun | |
235 | ||
236 | @deftypefun {HIST_ENTRY *} history_get (int offset) | |
237 | Return the history entry at position @var{offset}, starting from | |
238 | @code{history_base} (@pxref{History Variables}). | |
239 | If there is no entry there, or if @var{offset} | |
240 | is greater than the history length, return a @code{NULL} pointer. | |
241 | @end deftypefun | |
242 | ||
243 | @deftypefun time_t history_get_time (HIST_ENTRY *entry) | |
244 | Return the time stamp associated with the history entry @var{entry}. | |
245 | @end deftypefun | |
246 | ||
247 | @deftypefun int history_total_bytes (void) | |
248 | Return the number of bytes that the primary history entries are using. | |
249 | This function returns the sum of the lengths of all the lines in the | |
250 | history. | |
251 | @end deftypefun | |
252 | ||
253 | @node Moving Around the History List | |
254 | @subsection Moving Around the History List | |
255 | ||
256 | These functions allow the current index into the history list to be | |
257 | set or changed. | |
258 | ||
259 | @deftypefun int history_set_pos (int pos) | |
260 | Set the current history offset to @var{pos}, an absolute index | |
261 | into the list. | |
262 | Returns 1 on success, 0 if @var{pos} is less than zero or greater | |
263 | than the number of history entries. | |
264 | @end deftypefun | |
265 | ||
266 | @deftypefun {HIST_ENTRY *} previous_history (void) | |
267 | Back up the current history offset to the previous history entry, and | |
268 | return a pointer to that entry. If there is no previous entry, return | |
269 | a @code{NULL} pointer. | |
270 | @end deftypefun | |
271 | ||
272 | @deftypefun {HIST_ENTRY *} next_history (void) | |
273 | Move the current history offset forward to the next history entry, and | |
274 | return the a pointer to that entry. If there is no next entry, return | |
275 | a @code{NULL} pointer. | |
276 | @end deftypefun | |
277 | ||
278 | @node Searching the History List | |
279 | @subsection Searching the History List | |
280 | @cindex History Searching | |
281 | ||
282 | These functions allow searching of the history list for entries containing | |
283 | a specific string. Searching may be performed both forward and backward | |
284 | from the current history position. The search may be @dfn{anchored}, | |
285 | meaning that the string must match at the beginning of the history entry. | |
286 | @cindex anchored search | |
287 | ||
288 | @deftypefun int history_search (const char *string, int direction) | |
289 | Search the history for @var{string}, starting at the current history offset. | |
290 | If @var{direction} is less than 0, then the search is through | |
291 | previous entries, otherwise through subsequent entries. | |
292 | If @var{string} is found, then | |
293 | the current history index is set to that history entry, and the value | |
294 | returned is the offset in the line of the entry where | |
295 | @var{string} was found. Otherwise, nothing is changed, and a -1 is | |
296 | returned. | |
297 | @end deftypefun | |
298 | ||
299 | @deftypefun int history_search_prefix (const char *string, int direction) | |
300 | Search the history for @var{string}, starting at the current history | |
301 | offset. The search is anchored: matching lines must begin with | |
302 | @var{string}. If @var{direction} is less than 0, then the search is | |
303 | through previous entries, otherwise through subsequent entries. | |
304 | If @var{string} is found, then the | |
305 | current history index is set to that entry, and the return value is 0. | |
306 | Otherwise, nothing is changed, and a -1 is returned. | |
307 | @end deftypefun | |
308 | ||
309 | @deftypefun int history_search_pos (const char *string, int direction, int pos) | |
310 | Search for @var{string} in the history list, starting at @var{pos}, an | |
311 | absolute index into the list. If @var{direction} is negative, the search | |
312 | proceeds backward from @var{pos}, otherwise forward. Returns the absolute | |
313 | index of the history element where @var{string} was found, or -1 otherwise. | |
314 | @end deftypefun | |
315 | ||
316 | @node Managing the History File | |
317 | @subsection Managing the History File | |
318 | ||
319 | The History library can read the history from and write it to a file. | |
320 | This section documents the functions for managing a history file. | |
321 | ||
322 | @deftypefun int read_history (const char *filename) | |
323 | Add the contents of @var{filename} to the history list, a line at a time. | |
324 | If @var{filename} is @code{NULL}, then read from @file{~/.history}. | |
325 | Returns 0 if successful, or @code{errno} if not. | |
326 | @end deftypefun | |
327 | ||
328 | @deftypefun int read_history_range (const char *filename, int from, int to) | |
329 | Read a range of lines from @var{filename}, adding them to the history list. | |
330 | Start reading at line @var{from} and end at @var{to}. | |
331 | If @var{from} is zero, start at the beginning. If @var{to} is less than | |
332 | @var{from}, then read until the end of the file. If @var{filename} is | |
333 | @code{NULL}, then read from @file{~/.history}. Returns 0 if successful, | |
334 | or @code{errno} if not. | |
335 | @end deftypefun | |
336 | ||
337 | @deftypefun int write_history (const char *filename) | |
338 | Write the current history to @var{filename}, overwriting @var{filename} | |
339 | if necessary. | |
340 | If @var{filename} is @code{NULL}, then write the history list to | |
341 | @file{~/.history}. | |
342 | Returns 0 on success, or @code{errno} on a read or write error. | |
343 | @end deftypefun | |
344 | ||
345 | @deftypefun int append_history (int nelements, const char *filename) | |
346 | Append the last @var{nelements} of the history list to @var{filename}. | |
347 | If @var{filename} is @code{NULL}, then append to @file{~/.history}. | |
348 | Returns 0 on success, or @code{errno} on a read or write error. | |
349 | @end deftypefun | |
350 | ||
351 | @deftypefun int history_truncate_file (const char *filename, int nlines) | |
352 | Truncate the history file @var{filename}, leaving only the last | |
353 | @var{nlines} lines. | |
354 | If @var{filename} is @code{NULL}, then @file{~/.history} is truncated. | |
355 | Returns 0 on success, or @code{errno} on failure. | |
356 | @end deftypefun | |
357 | ||
358 | @node History Expansion | |
359 | @subsection History Expansion | |
360 | ||
361 | These functions implement history expansion. | |
362 | ||
363 | @deftypefun int history_expand (char *string, char **output) | |
364 | Expand @var{string}, placing the result into @var{output}, a pointer | |
365 | to a string (@pxref{History Interaction}). Returns: | |
366 | @table @code | |
367 | @item 0 | |
368 | If no expansions took place (or, if the only change in | |
369 | the text was the removal of escape characters preceding the history expansion | |
370 | character); | |
371 | @item 1 | |
372 | if expansions did take place; | |
373 | @item -1 | |
374 | if there was an error in expansion; | |
375 | @item 2 | |
376 | if the returned line should be displayed, but not executed, | |
377 | as with the @code{:p} modifier (@pxref{Modifiers}). | |
378 | @end table | |
379 | ||
380 | If an error ocurred in expansion, then @var{output} contains a descriptive | |
381 | error message. | |
382 | @end deftypefun | |
383 | ||
384 | @deftypefun {char *} get_history_event (const char *string, int *cindex, int qchar) | |
385 | Returns the text of the history event beginning at @var{string} + | |
386 | @var{*cindex}. @var{*cindex} is modified to point to after the event | |
387 | specifier. At function entry, @var{cindex} points to the index into | |
388 | @var{string} where the history event specification begins. @var{qchar} | |
389 | is a character that is allowed to end the event specification in addition | |
390 | to the ``normal'' terminating characters. | |
391 | @end deftypefun | |
392 | ||
393 | @deftypefun {char **} history_tokenize (const char *string) | |
394 | Return an array of tokens parsed out of @var{string}, much as the | |
395 | shell might. The tokens are split on the characters in the | |
396 | @var{history_word_delimiters} variable, | |
397 | and shell quoting conventions are obeyed. | |
398 | @end deftypefun | |
399 | ||
400 | @deftypefun {char *} history_arg_extract (int first, int last, const char *string) | |
401 | Extract a string segment consisting of the @var{first} through @var{last} | |
402 | arguments present in @var{string}. Arguments are split using | |
403 | @code{history_tokenize}. | |
404 | @end deftypefun | |
405 | ||
406 | @node History Variables | |
407 | @section History Variables | |
408 | ||
409 | This section describes the externally-visible variables exported by | |
410 | the @sc{gnu} History Library. | |
411 | ||
412 | @deftypevar int history_base | |
413 | The logical offset of the first entry in the history list. | |
414 | @end deftypevar | |
415 | ||
416 | @deftypevar int history_length | |
417 | The number of entries currently stored in the history list. | |
418 | @end deftypevar | |
419 | ||
420 | @deftypevar int history_max_entries | |
421 | The maximum number of history entries. This must be changed using | |
422 | @code{stifle_history()}. | |
423 | @end deftypevar | |
424 | ||
425 | @deftypevar int history_write_timestamps | |
426 | If non-zero, timestamps are written to the history file, so they can be | |
427 | preserved between sessions. The default value is 0, meaning that | |
428 | timestamps are not saved. | |
429 | @end deftypevar | |
430 | ||
431 | @deftypevar char history_expansion_char | |
432 | The character that introduces a history event. The default is @samp{!}. | |
433 | Setting this to 0 inhibits history expansion. | |
434 | @end deftypevar | |
435 | ||
436 | @deftypevar char history_subst_char | |
437 | The character that invokes word substitution if found at the start of | |
438 | a line. The default is @samp{^}. | |
439 | @end deftypevar | |
440 | ||
441 | @deftypevar char history_comment_char | |
442 | During tokenization, if this character is seen as the first character | |
443 | of a word, then it and all subsequent characters up to a newline are | |
444 | ignored, suppressing history expansion for the remainder of the line. | |
445 | This is disabled by default. | |
446 | @end deftypevar | |
447 | ||
448 | @deftypevar {char *} history_word_delimiters | |
449 | The characters that separate tokens for @code{history_tokenize()}. | |
450 | The default value is @code{" \t\n()<>;&|"}. | |
451 | @end deftypevar | |
452 | ||
453 | @deftypevar {char *} history_search_delimiter_chars | |
454 | The list of additional characters which can delimit a history search | |
455 | string, in addition to space, TAB, @samp{:} and @samp{?} in the case of | |
456 | a substring search. The default is empty. | |
457 | @end deftypevar | |
458 | ||
459 | @deftypevar {char *} history_no_expand_chars | |
460 | The list of characters which inhibit history expansion if found immediately | |
461 | following @var{history_expansion_char}. The default is space, tab, newline, | |
462 | carriage return, and @samp{=}. | |
463 | @end deftypevar | |
464 | ||
465 | @deftypevar int history_quotes_inhibit_expansion | |
466 | If non-zero, single-quoted words are not scanned for the history expansion | |
467 | character. The default value is 0. | |
468 | @end deftypevar | |
469 | ||
470 | @deftypevar {rl_linebuf_func_t *} history_inhibit_expansion_function | |
471 | This should be set to the address of a function that takes two arguments: | |
472 | a @code{char *} (@var{string}) | |
473 | and an @code{int} index into that string (@var{i}). | |
474 | It should return a non-zero value if the history expansion starting at | |
475 | @var{string[i]} should not be performed; zero if the expansion should | |
476 | be done. | |
477 | It is intended for use by applications like Bash that use the history | |
478 | expansion character for additional purposes. | |
479 | By default, this variable is set to @code{NULL}. | |
480 | @end deftypevar | |
481 | ||
482 | @node History Programming Example | |
483 | @section History Programming Example | |
484 | ||
485 | The following program demonstrates simple use of the @sc{gnu} History Library. | |
486 | ||
487 | @smallexample | |
488 | #include <stdio.h> | |
489 | #include <readline/history.h> | |
490 | ||
491 | main (argc, argv) | |
492 | int argc; | |
493 | char **argv; | |
494 | @{ | |
495 | char line[1024], *t; | |
496 | int len, done = 0; | |
497 | ||
498 | line[0] = 0; | |
499 | ||
500 | using_history (); | |
501 | while (!done) | |
502 | @{ | |
503 | printf ("history$ "); | |
504 | fflush (stdout); | |
505 | t = fgets (line, sizeof (line) - 1, stdin); | |
506 | if (t && *t) | |
507 | @{ | |
508 | len = strlen (t); | |
509 | if (t[len - 1] == '\n') | |
510 | t[len - 1] = '\0'; | |
511 | @} | |
512 | ||
513 | if (!t) | |
514 | strcpy (line, "quit"); | |
515 | ||
516 | if (line[0]) | |
517 | @{ | |
518 | char *expansion; | |
519 | int result; | |
520 | ||
521 | result = history_expand (line, &expansion); | |
522 | if (result) | |
523 | fprintf (stderr, "%s\n", expansion); | |
524 | ||
525 | if (result < 0 || result == 2) | |
526 | @{ | |
527 | free (expansion); | |
528 | continue; | |
529 | @} | |
530 | ||
531 | add_history (expansion); | |
532 | strncpy (line, expansion, sizeof (line) - 1); | |
533 | free (expansion); | |
534 | @} | |
535 | ||
536 | if (strcmp (line, "quit") == 0) | |
537 | done = 1; | |
538 | else if (strcmp (line, "save") == 0) | |
539 | write_history ("history_file"); | |
540 | else if (strcmp (line, "read") == 0) | |
541 | read_history ("history_file"); | |
542 | else if (strcmp (line, "list") == 0) | |
543 | @{ | |
544 | register HIST_ENTRY **the_list; | |
545 | register int i; | |
546 | ||
547 | the_list = history_list (); | |
548 | if (the_list) | |
549 | for (i = 0; the_list[i]; i++) | |
550 | printf ("%d: %s\n", i + history_base, the_list[i]->line); | |
551 | @} | |
552 | else if (strncmp (line, "delete", 6) == 0) | |
553 | @{ | |
554 | int which; | |
555 | if ((sscanf (line + 6, "%d", &which)) == 1) | |
556 | @{ | |
557 | HIST_ENTRY *entry = remove_history (which); | |
558 | if (!entry) | |
559 | fprintf (stderr, "No such entry %d\n", which); | |
560 | else | |
561 | @{ | |
562 | free (entry->line); | |
563 | free (entry); | |
564 | @} | |
565 | @} | |
566 | else | |
567 | @{ | |
568 | fprintf (stderr, "non-numeric arg given to `delete'\n"); | |
569 | @} | |
570 | @} | |
571 | @} | |
572 | @} | |
573 | @end smallexample |