1: @ignore
2: This file documents the user interface to the GNU History library.
3:
4: Copyright (C) 1988-2014 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 occurred 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:
430: The current timestamp format uses the value of @var{history_comment_char}
431: to delimit timestamp entries in the history file. If that variable does
432: not have a value (the default), timestamps will not be written.
433: @end deftypevar
434:
435: @deftypevar char history_expansion_char
436: The character that introduces a history event. The default is @samp{!}.
437: Setting this to 0 inhibits history expansion.
438: @end deftypevar
439:
440: @deftypevar char history_subst_char
441: The character that invokes word substitution if found at the start of
442: a line. The default is @samp{^}.
443: @end deftypevar
444:
445: @deftypevar char history_comment_char
446: During tokenization, if this character is seen as the first character
447: of a word, then it and all subsequent characters up to a newline are
448: ignored, suppressing history expansion for the remainder of the line.
449: This is disabled by default.
450: @end deftypevar
451:
452: @deftypevar {char *} history_word_delimiters
453: The characters that separate tokens for @code{history_tokenize()}.
454: The default value is @code{" \t\n()<>;&|"}.
455: @end deftypevar
456:
457: @deftypevar {char *} history_search_delimiter_chars
458: The list of additional characters which can delimit a history search
459: string, in addition to space, TAB, @samp{:} and @samp{?} in the case of
460: a substring search. The default is empty.
461: @end deftypevar
462:
463: @deftypevar {char *} history_no_expand_chars
464: The list of characters which inhibit history expansion if found immediately
465: following @var{history_expansion_char}. The default is space, tab, newline,
466: carriage return, and @samp{=}.
467: @end deftypevar
468:
469: @deftypevar int history_quotes_inhibit_expansion
470: If non-zero, single-quoted words are not scanned for the history expansion
471: character. The default value is 0.
472: @end deftypevar
473:
474: @deftypevar {rl_linebuf_func_t *} history_inhibit_expansion_function
475: This should be set to the address of a function that takes two arguments:
476: a @code{char *} (@var{string})
477: and an @code{int} index into that string (@var{i}).
478: It should return a non-zero value if the history expansion starting at
479: @var{string[i]} should not be performed; zero if the expansion should
480: be done.
481: It is intended for use by applications like Bash that use the history
482: expansion character for additional purposes.
483: By default, this variable is set to @code{NULL}.
484: @end deftypevar
485:
486: @node History Programming Example
487: @section History Programming Example
488:
489: The following program demonstrates simple use of the @sc{gnu} History Library.
490:
491: @smallexample
492: #include <stdio.h>
493: #include <readline/history.h>
494:
495: main (argc, argv)
496: int argc;
497: char **argv;
498: @{
499: char line[1024], *t;
500: int len, done = 0;
501:
502: line[0] = 0;
503:
504: using_history ();
505: while (!done)
506: @{
507: printf ("history$ ");
508: fflush (stdout);
509: t = fgets (line, sizeof (line) - 1, stdin);
510: if (t && *t)
511: @{
512: len = strlen (t);
513: if (t[len - 1] == '\n')
514: t[len - 1] = '\0';
515: @}
516:
517: if (!t)
518: strcpy (line, "quit");
519:
520: if (line[0])
521: @{
522: char *expansion;
523: int result;
524:
525: result = history_expand (line, &expansion);
526: if (result)
527: fprintf (stderr, "%s\n", expansion);
528:
529: if (result < 0 || result == 2)
530: @{
531: free (expansion);
532: continue;
533: @}
534:
535: add_history (expansion);
536: strncpy (line, expansion, sizeof (line) - 1);
537: free (expansion);
538: @}
539:
540: if (strcmp (line, "quit") == 0)
541: done = 1;
542: else if (strcmp (line, "save") == 0)
543: write_history ("history_file");
544: else if (strcmp (line, "read") == 0)
545: read_history ("history_file");
546: else if (strcmp (line, "list") == 0)
547: @{
548: register HIST_ENTRY **the_list;
549: register int i;
550:
551: the_list = history_list ();
552: if (the_list)
553: for (i = 0; the_list[i]; i++)
554: printf ("%d: %s\n", i + history_base, the_list[i]->line);
555: @}
556: else if (strncmp (line, "delete", 6) == 0)
557: @{
558: int which;
559: if ((sscanf (line + 6, "%d", &which)) == 1)
560: @{
561: HIST_ENTRY *entry = remove_history (which);
562: if (!entry)
563: fprintf (stderr, "No such entry %d\n", which);
564: else
565: @{
566: free (entry->line);
567: free (entry);
568: @}
569: @}
570: else
571: @{
572: fprintf (stderr, "non-numeric arg given to `delete'\n");
573: @}
574: @}
575: @}
576: @}
577: @end smallexample
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