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[project @ 1997-05-22 20:58:07 by jwe]
author | jwe |
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date | Thu, 22 May 1997 20:59:27 +0000 |
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children | 3001e15555e9 |
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1 @ignore | |
2 This file documents the user interface to the GNU History library. | |
3 | |
4 Copyright (C) 1988, 1991, 1994, 1996 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 GNU History Library. | |
31 It should be considered a technical guide. | |
32 For information on the interactive use of 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 GNU History | |
47 library is able to keep track of those lines, associate arbitrary data with | |
48 each line, and utilize information from previous lines in composing new | |
49 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 @node History Storage | |
70 @section History Storage | |
71 | |
72 The history list is an array of history entries. A history entry is | |
73 declared as follows: | |
74 | |
75 @example | |
76 typedef struct _hist_entry @{ | |
77 char *line; | |
78 char *data; | |
79 @} HIST_ENTRY; | |
80 @end example | |
81 | |
82 The history list itself might therefore be declared as | |
83 | |
84 @example | |
85 HIST_ENTRY **the_history_list; | |
86 @end example | |
87 | |
88 The state of the History library is encapsulated into a single structure: | |
89 | |
90 @example | |
91 /* A structure used to pass the current state of the history stuff around. */ | |
92 typedef struct _hist_state @{ | |
93 HIST_ENTRY **entries; /* Pointer to the entries themselves. */ | |
94 int offset; /* The location pointer within this array. */ | |
95 int length; /* Number of elements within this array. */ | |
96 int size; /* Number of slots allocated to this array. */ | |
97 int flags; | |
98 @} HISTORY_STATE; | |
99 @end example | |
100 | |
101 If the flags member includes @code{HS_STIFLED}, the history has been | |
102 stifled. | |
103 | |
104 @node History Functions | |
105 @section History Functions | |
106 | |
107 This section describes the calling sequence for the various functions | |
108 present in GNU History. | |
109 | |
110 @menu | |
111 * Initializing History and State Management:: Functions to call when you | |
112 want to use history in a | |
113 program. | |
114 * History List Management:: Functions used to manage the list | |
115 of history entries. | |
116 * Information About the History List:: Functions returning information about | |
117 the history list. | |
118 * Moving Around the History List:: Functions used to change the position | |
119 in the history list. | |
120 * Searching the History List:: Functions to search the history list | |
121 for entries containing a string. | |
122 * Managing the History File:: Functions that read and write a file | |
123 containing the history list. | |
124 * History Expansion:: Functions to perform csh-like history | |
125 expansion. | |
126 @end menu | |
127 | |
128 @node Initializing History and State Management | |
129 @subsection Initializing History and State Management | |
130 | |
131 This section describes functions used to initialize and manage | |
132 the state of the History library when you want to use the history | |
133 functions in your program. | |
134 | |
135 @deftypefun void using_history () | |
136 Begin a session in which the history functions might be used. This | |
137 initializes the interactive variables. | |
138 @end deftypefun | |
139 | |
140 @deftypefun {HISTORY_STATE *} history_get_history_state () | |
141 Return a structure describing the current state of the input history. | |
142 @end deftypefun | |
143 | |
144 @deftypefun void history_set_history_state (HISTORY_STATE *state) | |
145 Set the state of the history list according to @var{state}. | |
146 @end deftypefun | |
147 | |
148 @node History List Management | |
149 @subsection History List Management | |
150 | |
151 These functions manage individual entries on the history list, or set | |
152 parameters managing the list itself. | |
153 | |
154 @deftypefun void add_history (char *string) | |
155 Place @var{string} at the end of the history list. The associated data | |
156 field (if any) is set to @code{NULL}. | |
157 @end deftypefun | |
158 | |
159 @deftypefun {HIST_ENTRY *} remove_history (int which) | |
160 Remove history entry at offset @var{which} from the history. The | |
161 removed element is returned so you can free the line, data, | |
162 and containing structure. | |
163 @end deftypefun | |
164 | |
165 @deftypefun {HIST_ENTRY *} replace_history_entry (int which, char *line, char *data) | |
166 Make the history entry at offset @var{which} have @var{line} and @var{data}. | |
167 This returns the old entry so you can dispose of the data. In the case | |
168 of an invalid @var{which}, a @code{NULL} pointer is returned. | |
169 @end deftypefun | |
170 | |
171 @deftypefun void clear_history () | |
172 Clear the history list by deleting all the entries. | |
173 @end deftypefun | |
174 | |
175 @deftypefun void stifle_history (int max) | |
176 Stifle the history list, remembering only the last @var{max} entries. | |
177 @end deftypefun | |
178 | |
179 @deftypefun int unstifle_history () | |
180 Stop stifling the history. This returns the previous amount the | |
181 history was stifled. The value is positive if the history was | |
182 stifled, negative if it wasn't. | |
183 @end deftypefun | |
184 | |
185 @deftypefun int history_is_stifled () | |
186 Returns non-zero if the history is stifled, zero if it is not. | |
187 @end deftypefun | |
188 | |
189 @node Information About the History List | |
190 @subsection Information About the History List | |
191 | |
192 These functions return information about the entire history list or | |
193 individual list entries. | |
194 | |
195 @deftypefun {HIST_ENTRY **} history_list () | |
196 Return a @code{NULL} terminated array of @code{HIST_ENTRY} which is the | |
197 current input history. Element 0 of this list is the beginning of time. | |
198 If there is no history, return @code{NULL}. | |
199 @end deftypefun | |
200 | |
201 @deftypefun int where_history () | |
202 Returns the offset of the current history element. | |
203 @end deftypefun | |
204 | |
205 @deftypefun {HIST_ENTRY *} current_history () | |
206 Return the history entry at the current position, as determined by | |
207 @code{where_history ()}. If there is no entry there, return a @code{NULL} | |
208 pointer. | |
209 @end deftypefun | |
210 | |
211 @deftypefun {HIST_ENTRY *} history_get (int offset) | |
212 Return the history entry at position @var{offset}, starting from | |
213 @code{history_base}. If there is no entry there, or if @var{offset} | |
214 is greater than the history length, return a @code{NULL} pointer. | |
215 @end deftypefun | |
216 | |
217 @deftypefun int history_total_bytes () | |
218 Return the number of bytes that the primary history entries are using. | |
219 This function returns the sum of the lengths of all the lines in the | |
220 history. | |
221 @end deftypefun | |
222 | |
223 @node Moving Around the History List | |
224 @subsection Moving Around the History List | |
225 | |
226 These functions allow the current index into the history list to be | |
227 set or changed. | |
228 | |
229 @deftypefun int history_set_pos (int pos) | |
230 Set the position in the history list to @var{pos}, an absolute index | |
231 into the list. | |
232 @end deftypefun | |
233 | |
234 @deftypefun {HIST_ENTRY *} previous_history () | |
235 Back up the current history offset to the previous history entry, and | |
236 return a pointer to that entry. If there is no previous entry, return | |
237 a @code{NULL} pointer. | |
238 @end deftypefun | |
239 | |
240 @deftypefun {HIST_ENTRY *} next_history () | |
241 Move the current history offset forward to the next history entry, and | |
242 return the a pointer to that entry. If there is no next entry, return | |
243 a @code{NULL} pointer. | |
244 @end deftypefun | |
245 | |
246 @node Searching the History List | |
247 @subsection Searching the History List | |
248 @cindex History Searching | |
249 | |
250 These functions allow searching of the history list for entries containing | |
251 a specific string. Searching may be performed both forward and backward | |
252 from the current history position. The search may be @dfn{anchored}, | |
253 meaning that the string must match at the beginning of the history entry. | |
254 @cindex anchored search | |
255 | |
256 @deftypefun int history_search (char *string, int direction) | |
257 Search the history for @var{string}, starting at the current history | |
258 offset. If @var{direction} < 0, then the search is through previous entries, | |
259 else through subsequent. If @var{string} is found, then | |
260 the current history index is set to that history entry, and the value | |
261 returned is the offset in the line of the entry where | |
262 @var{string} was found. Otherwise, nothing is changed, and a -1 is | |
263 returned. | |
264 @end deftypefun | |
265 | |
266 @deftypefun int history_search_prefix (char *string, int direction) | |
267 Search the history for @var{string}, starting at the current history | |
268 offset. The search is anchored: matching lines must begin with | |
269 @var{string}. If @var{direction} < 0, then the search is through previous | |
270 entries, else through subsequent. If @var{string} is found, then the | |
271 current history index is set to that entry, and the return value is 0. | |
272 Otherwise, nothing is changed, and a -1 is returned. | |
273 @end deftypefun | |
274 | |
275 @deftypefun int history_search_pos (char *string, int direction, int pos) | |
276 Search for @var{string} in the history list, starting at @var{pos}, an | |
277 absolute index into the list. If @var{direction} is negative, the search | |
278 proceeds backward from @var{pos}, otherwise forward. Returns the absolute | |
279 index of the history element where @var{string} was found, or -1 otherwise. | |
280 @end deftypefun | |
281 | |
282 @node Managing the History File | |
283 @subsection Managing the History File | |
284 | |
285 The History library can read the history from and write it to a file. | |
286 This section documents the functions for managing a history file. | |
287 | |
288 @deftypefun int read_history (char *filename) | |
289 Add the contents of @var{filename} to the history list, a line at a | |
290 time. If @var{filename} is @code{NULL}, then read from | |
291 @file{~/.history}. Returns 0 if successful, or errno if not. | |
292 @end deftypefun | |
293 | |
294 @deftypefun int read_history_range (char *filename, int from, int to) | |
295 Read a range of lines from @var{filename}, adding them to the history list. | |
296 Start reading at line @var{from} and end at @var{to}. If | |
297 @var{from} is zero, start at the beginning. If @var{to} is less than | |
298 @var{from}, then read until the end of the file. If @var{filename} is | |
299 @code{NULL}, then read from @file{~/.history}. Returns 0 if successful, | |
300 or @code{errno} if not. | |
301 @end deftypefun | |
302 | |
303 @deftypefun int write_history (char *filename) | |
304 Write the current history to @var{filename}, overwriting @var{filename} | |
305 if necessary. If @var{filename} is | |
306 @code{NULL}, then write the history list to @file{~/.history}. Values | |
307 returned are as in @code{read_history ()}. | |
308 @end deftypefun | |
309 | |
310 @deftypefun int append_history (int nelements, char *filename) | |
311 Append the last @var{nelements} of the history list to @var{filename}. | |
312 @end deftypefun | |
313 | |
314 @deftypefun int history_truncate_file (char *filename, int nlines) | |
315 Truncate the history file @var{filename}, leaving only the last | |
316 @var{nlines} lines. | |
317 @end deftypefun | |
318 | |
319 @node History Expansion | |
320 @subsection History Expansion | |
321 | |
322 These functions implement @code{csh}-like history expansion. | |
323 | |
324 @deftypefun int history_expand (char *string, char **output) | |
325 Expand @var{string}, placing the result into @var{output}, a pointer | |
326 to a string (@pxref{History Interaction}). Returns: | |
327 @table @code | |
328 @item 0 | |
329 If no expansions took place (or, if the only change in | |
330 the text was the de-slashifying of the history expansion | |
331 character); | |
332 @item 1 | |
333 if expansions did take place; | |
334 @item -1 | |
335 if there was an error in expansion; | |
336 @item 2 | |
337 if the returned line should only be displayed, but not executed, | |
338 as with the @code{:p} modifier (@pxref{Modifiers}). | |
339 @end table | |
340 | |
341 If an error ocurred in expansion, then @var{output} contains a descriptive | |
342 error message. | |
343 @end deftypefun | |
344 | |
345 @deftypefun {char *} history_arg_extract (int first, int last, char *string) | |
346 Extract a string segment consisting of the @var{first} through @var{last} | |
347 arguments present in @var{string}. Arguments are broken up as in Bash. | |
348 @end deftypefun | |
349 | |
350 @deftypefun {char *} get_history_event (char *string, int *cindex, int qchar) | |
351 Returns the text of the history event beginning at @var{string} + | |
352 @var{*cindex}. @var{*cindex} is modified to point to after the event | |
353 specifier. At function entry, @var{cindex} points to the index into | |
354 @var{string} where the history event specification begins. @var{qchar} | |
355 is a character that is allowed to end the event specification in addition | |
356 to the ``normal'' terminating characters. | |
357 @end deftypefun | |
358 | |
359 @deftypefun {char **} history_tokenize (char *string) | |
360 Return an array of tokens parsed out of @var{string}, much as the | |
361 shell might. The tokens are split on white space and on the | |
362 characters @code{()<>;&|$}, and shell quoting conventions are | |
363 obeyed. | |
364 @end deftypefun | |
365 | |
366 @node History Variables | |
367 @section History Variables | |
368 | |
369 This section describes the externally visible variables exported by | |
370 the GNU History Library. | |
371 | |
372 @deftypevar int history_base | |
373 The logical offset of the first entry in the history list. | |
374 @end deftypevar | |
375 | |
376 @deftypevar int history_length | |
377 The number of entries currently stored in the history list. | |
378 @end deftypevar | |
379 | |
380 @deftypevar int max_input_history | |
381 The maximum number of history entries. This must be changed using | |
382 @code{stifle_history ()}. | |
383 @end deftypevar | |
384 | |
385 @deftypevar char history_expansion_char | |
386 The character that starts a history event. The default is @samp{!}. | |
387 @end deftypevar | |
388 | |
389 @deftypevar char history_subst_char | |
390 The character that invokes word substitution if found at the start of | |
391 a line. The default is @samp{^}. | |
392 @end deftypevar | |
393 | |
394 @deftypevar char history_comment_char | |
395 During tokenization, if this character is seen as the first character | |
396 of a word, then it and all subsequent characters up to a newline are | |
397 ignored, suppressing history expansion for the remainder of the line. | |
398 This is disabled by default. | |
399 @end deftypevar | |
400 | |
401 @deftypevar {char *} history_no_expand_chars | |
402 The list of characters which inhibit history expansion if found immediately | |
403 following @var{history_expansion_char}. The default is whitespace and | |
404 @samp{=}. | |
405 @end deftypevar | |
406 | |
407 @deftypevar {char *} history_search_delimiter_chars | |
408 The list of additional characters which can delimit a history search | |
409 string, in addition to whitespace, @samp{:} and @samp{?} in the case of | |
410 a substring search. The default is empty. | |
411 @end deftypevar | |
412 | |
413 @deftypevar int history_quotes_inhibit_expansion | |
414 If non-zero, single-quoted words are not scanned for the history expansion | |
415 character. The default value is 0. | |
416 @end deftypevar | |
417 | |
418 @deftypevar {Function *} history_inhibit_expansion_function | |
419 This should be set to the address of a function that takes two arguments: | |
420 a @code{char *} (@var{string}) and an integer index into that string (@var{i}). | |
421 It should return a non-zero value if the history expansion starting at | |
422 @var{string[i]} should not be performed; zero if the expansion should | |
423 be done. | |
424 It is intended for use by applications like Bash that use the history | |
425 expansion character for additional purposes. | |
426 By default, this variable is set to NULL. | |
427 @end deftypevar | |
428 | |
429 @node History Programming Example | |
430 @section History Programming Example | |
431 | |
432 The following program demonstrates simple use of the GNU History Library. | |
433 | |
434 @smallexample | |
435 main () | |
436 @{ | |
437 char line[1024], *t; | |
438 int len, done = 0; | |
439 | |
440 line[0] = 0; | |
441 | |
442 using_history (); | |
443 while (!done) | |
444 @{ | |
445 printf ("history$ "); | |
446 fflush (stdout); | |
447 t = fgets (line, sizeof (line) - 1, stdin); | |
448 if (t && *t) | |
449 @{ | |
450 len = strlen (t); | |
451 if (t[len - 1] == '\n') | |
452 t[len - 1] = '\0'; | |
453 @} | |
454 | |
455 if (!t) | |
456 strcpy (line, "quit"); | |
457 | |
458 if (line[0]) | |
459 @{ | |
460 char *expansion; | |
461 int result; | |
462 | |
463 result = history_expand (line, &expansion); | |
464 if (result) | |
465 fprintf (stderr, "%s\n", expansion); | |
466 | |
467 if (result < 0 || result == 2) | |
468 @{ | |
469 free (expansion); | |
470 continue; | |
471 @} | |
472 | |
473 add_history (expansion); | |
474 strncpy (line, expansion, sizeof (line) - 1); | |
475 free (expansion); | |
476 @} | |
477 | |
478 if (strcmp (line, "quit") == 0) | |
479 done = 1; | |
480 else if (strcmp (line, "save") == 0) | |
481 write_history ("history_file"); | |
482 else if (strcmp (line, "read") == 0) | |
483 read_history ("history_file"); | |
484 else if (strcmp (line, "list") == 0) | |
485 @{ | |
486 register HIST_ENTRY **the_list; | |
487 register int i; | |
488 | |
489 the_list = history_list (); | |
490 if (the_list) | |
491 for (i = 0; the_list[i]; i++) | |
492 printf ("%d: %s\n", i + history_base, the_list[i]->line); | |
493 @} | |
494 else if (strncmp (line, "delete", 6) == 0) | |
495 @{ | |
496 int which; | |
497 if ((sscanf (line + 6, "%d", &which)) == 1) | |
498 @{ | |
499 HIST_ENTRY *entry = remove_history (which); | |
500 if (!entry) | |
501 fprintf (stderr, "No such entry %d\n", which); | |
502 else | |
503 @{ | |
504 free (entry->line); | |
505 free (entry); | |
506 @} | |
507 @} | |
508 else | |
509 @{ | |
510 fprintf (stderr, "non-numeric arg given to `delete'\n"); | |
511 @} | |
512 @} | |
513 @} | |
514 @} | |
515 @end smallexample |