1HISTORY(3) Library Functions Manual HISTORY(3)
2
6 history - GNU History Library
7
9 The GNU History Library is Copyright (C) 1989-2011 by the Free Software
10 Foundation, Inc.
11
13 Many programs read input from the user a line at a time. The GNU His‐
14 tory library is able to keep track of those lines, associate arbitrary
15 data with each line, and utilize information from previous lines in
16 composing new ones.
17
19 The history library supports a history expansion feature that is iden‐
20 tical to the history expansion in bash. This section describes what
21 syntax features are available.
22 History expansions introduce words from the history list into the input
24 stream, making it easy to repeat commands, insert the arguments to a
25 previous command into the current input line, or fix errors in previous
26 commands quickly.
27 History expansion is usually performed immediately after a complete
29 line is read. It takes place in two parts. The first is to determine
30 which line from the history list to use during substitution. The sec‐
31 ond is to select portions of that line for inclusion into the current
32 one. The line selected from the history is the event, and the portions
33 of that line that are acted upon are words. Various modifiers are
34 available to manipulate the selected words. The line is broken into
35 words in the same fashion as bash does when reading input, so that sev‐
36 eral words that would otherwise be separated are considered one word
37 when surrounded by quotes (see the description of history_tokenize()
38 below). History expansions are introduced by the appearance of the
39 history expansion character, which is ! by default. Only backslash (\)
40 and single quotes can quote the history expansion character.
41 Event Designators
43 An event designator is a reference to a command line entry in the his‐
44 tory list. Unless the reference is absolute, events are relative to
45 the current position in the history list.
46 ! Start a history substitution, except when followed by a blank,
48 newline, = or (.
49 !n Refer to command line n.
50 !-n Refer to the current command minus n.
51 !! Refer to the previous command. This is a synonym for `!-1'.
52 !string
53 Refer to the most recent command preceding the current position
54 in the history list starting with string.
55 !?string[?]
56 Refer to the most recent command preceding the current postition
57 in the history list containing string. The trailing ? may be
58 omitted if string is followed immediately by a newline.
59 ^string1^string2^
60 Quick substitution. Repeat the last command, replacing string1
61 with string2. Equivalent to ``!!:s/string1/string2/'' (see Mod‐
62 ifiers below).
63 !# The entire command line typed so far.
64 Word Designators
66 Word designators are used to select desired words from the event. A :
67 separates the event specification from the word designator. It may be
68 omitted if the word designator begins with a ^, $, *, -, or %. Words
69 are numbered from the beginning of the line, with the first word being
70 denoted by 0 (zero). Words are inserted into the current line sepa‐
71 rated by single spaces.
72 0 (zero)
74 The zeroth word. For the shell, this is the command word.
75 n The nth word.
76 ^ The first argument. That is, word 1.
77 $ The last argument.
78 % The word matched by the most recent `?string?' search.
79 x-y A range of words; `-y' abbreviates `0-y'.
80 * All of the words but the zeroth. This is a synonym for `1-$'.
81 It is not an error to use * if there is just one word in the
82 event; the empty string is returned in that case.
83 x* Abbreviates x-$.
84 x- Abbreviates x-$ like x*, but omits the last word.
85 If a word designator is supplied without an event specification, the
87 previous command is used as the event.
88 Modifiers
90 After the optional word designator, there may appear a sequence of one
91 or more of the following modifiers, each preceded by a `:'.
92 h Remove a trailing file name component, leaving only the head.
94 t Remove all leading file name components, leaving the tail.
95 r Remove a trailing suffix of the form .xxx, leaving the basename.
96 e Remove all but the trailing suffix.
97 p Print the new command but do not execute it.
98 q Quote the substituted words, escaping further substitutions.
99 x Quote the substituted words as with q, but break into words at
100 blanks and newlines.
101 s/old/new/
102 Substitute new for the first occurrence of old in the event
103 line. Any delimiter can be used in place of /. The final
104 delimiter is optional if it is the last character of the event
105 line. The delimiter may be quoted in old and new with a single
106 backslash. If & appears in new, it is replaced by old. A sin‐
107 gle backslash will quote the &. If old is null, it is set to
108 the last old substituted, or, if no previous history substitu‐
109 tions took place, the last string in a !?string[?] search.
110 & Repeat the previous substitution.
111 g Cause changes to be applied over the entire event line. This is
112 used in conjunction with `:s' (e.g., `:gs/old/new/') or `:&'.
113 If used with `:s', any delimiter can be used in place of /, and
114 the final delimiter is optional if it is the last character of
115 the event line. An a may be used as a synonym for g.
116 G Apply the following `s' modifier once to each word in the event
117 line.
118
120 This section describes how to use the History library in other pro‐
121 grams.
122 Introduction to History
124 The programmer using the History library has available functions for
125 remembering lines on a history list, associating arbitrary data with a
126 line, removing lines from the list, searching through the list for a
127 line containing an arbitrary text string, and referencing any line in
128 the list directly. In addition, a history expansion function is avail‐
129 able which provides for a consistent user interface across different
130 programs.
131 The user using programs written with the History library has the bene‐
133 fit of a consistent user interface with a set of well-known commands
134 for manipulating the text of previous lines and using that text in new
135 commands. The basic history manipulation commands are identical to the
136 history substitution provided by bash.
137 If the programmer desires, he can use the Readline library, which
139 includes some history manipulation by default, and has the added advan‐
140 tage of command line editing.
141 Before declaring any functions using any functionality the History
143 library provides in other code, an application writer should include
144 the file <readline/history.h> in any file that uses the History
145 library's features. It supplies extern declarations for all of the
146 library's public functions and variables, and declares all of the pub‐
147 lic data structures.
148 History Storage
151 The history list is an array of history entries. A history entry is
152 declared as follows:
153 typedef void * histdata_t;
155 typedef struct _hist_entry {
157 char *line;
158 char *timestamp;
159 histdata_t data;
160 } HIST_ENTRY;
161 The history list itself might therefore be declared as
163 HIST_ENTRY ** the_history_list;
165 The state of the History library is encapsulated into a single struc‐
167 ture:
168 /*
170 * A structure used to pass around the current state of the history.
171 */
172 typedef struct _hist_state {
173 HIST_ENTRY **entries; /* Pointer to the entries themselves. */
174 int offset; /* The location pointer within this array. */
175 int length; /* Number of elements within this array. */
176 int size; /* Number of slots allocated to this array. */
177 int flags;
178 } HISTORY_STATE;
179 If the flags member includes HS_STIFLED, the history has been stifled.
181
183 This section describes the calling sequence for the various functions
184 exported by the GNU History library.
185 Initializing History and State Management
187 This section describes functions used to initialize and manage the
188 state of the History library when you want to use the history functions
189 in your program.
190 void using_history (void)
192 Begin a session in which the history functions might be used. This
193 initializes the interactive variables.
194 HISTORY_STATE * history_get_history_state (void)
196 Return a structure describing the current state of the input history.
197 void history_set_history_state (HISTORY_STATE *state)
199 Set the state of the history list according to state.
200 History List Management
203 These functions manage individual entries on the history list, or set
204 parameters managing the list itself.
205 void add_history (const char *string)
207 Place string at the end of the history list. The associated data field
208 (if any) is set to NULL.
209 void add_history_time (const char *string)
211 Change the time stamp associated with the most recent history entry to
212 string.
213 HIST_ENTRY * remove_history (int which)
215 Remove history entry at offset which from the history. The removed
216 element is returned so you can free the line, data, and containing
217 structure.
218 histdata_t free_history_entry (HIST_ENTRY *histent)
220 Free the history entry histent and any history library private data
221 associated with it. Returns the application-specific data so the call‐
222 er can dispose of it.
223 HIST_ENTRY * replace_history_entry (int which, const char *line, hist‐
225 data_t data)
226 Make the history entry at offset which have line and data. This
227 returns the old entry so the caller can dispose of any application-spe‐
228 cific data. In the case of an invalid which, a NULL pointer is
229 returned.
230 void clear_history (void)
232 Clear the history list by deleting all the entries.
233 void stifle_history (int max)
235 Stifle the history list, remembering only the last max entries.
236 int unstifle_history (void)
238 Stop stifling the history. This returns the previously-set maximum
239 number of history entries (as set by stifle_history()). history was
240 stifled. The value is positive if the history was stifled, negative if
241 it wasn't.
242 int history_is_stifled (void)
244 Returns non-zero if the history is stifled, zero if it is not.
245 Information About the History List
248 These functions return information about the entire history list or
249 individual list entries.
250 HIST_ENTRY ** history_list (void)
252 Return a NULL terminated array of HIST_ENTRY * which is the current
253 input history. Element 0 of this list is the beginning of time. If
254 there is no history, return NULL.
255 int where_history (void)
257 Returns the offset of the current history element.
258 HIST_ENTRY * current_history (void)
260 Return the history entry at the current position, as determined by
261 where_history(). If there is no entry there, return a NULL pointer.
262 HIST_ENTRY * history_get (int offset)
264 Return the history entry at position offset, starting from his‐
265 tory_base. If there is no entry there, or if offset is greater than
266 the history length, return a NULL pointer.
267 time_t history_get_time (HIST_ENTRY *)
269 Return the time stamp associated with the history entry passed as the
270 argument.
271 int history_total_bytes (void)
273 Return the number of bytes that the primary history entries are using.
274 This function returns the sum of the lengths of all the lines in the
275 history.
276 Moving Around the History List
279 These functions allow the current index into the history list to be set
280 or changed.
281 int history_set_pos (int pos)
283 Set the current history offset to pos, an absolute index into the list.
284 Returns 1 on success, 0 if pos is less than zero or greater than the
285 number of history entries.
286 HIST_ENTRY * previous_history (void)
288 Back up the current history offset to the previous history entry, and
289 return a pointer to that entry. If there is no previous entry, return
290 a NULL pointer.
291 HIST_ENTRY * next_history (void)
293 Move the current history offset forward to the next history entry, and
294 return the a pointer to that entry. If there is no next entry, return
295 a NULL pointer.
296 Searching the History List
299 These functions allow searching of the history list for entries con‐
300 taining a specific string. Searching may be performed both forward and
301 backward from the current history position. The search may be
302 anchored, meaning that the string must match at the beginning of the
303 history entry.
304 int history_search (const char *string, int direction)
306 Search the history for string, starting at the current history offset.
307 If direction is less than 0, then the search is through previous
308 entries, otherwise through subsequent entries. If string is found,
309 then the current history index is set to that history entry, and the
310 value returned is the offset in the line of the entry where string was
311 found. Otherwise, nothing is changed, and a -1 is returned.
312 int history_search_prefix (const char *string, int direction)
314 Search the history for string, starting at the current history offset.
315 The search is anchored: matching lines must begin with string. If
316 direction is less than 0, then the search is through previous entries,
317 otherwise through subsequent entries. If string is found, then the
318 current history index is set to that entry, and the return value is 0.
319 Otherwise, nothing is changed, and a -1 is returned.
320 int history_search_pos (const char *string, int direction, int pos)
322 Search for string in the history list, starting at pos, an absolute
323 index into the list. If direction is negative, the search proceeds
324 backward from pos, otherwise forward. Returns the absolute index of
325 the history element where string was found, or -1 otherwise.
326 Managing the History File
329 The History library can read the history from and write it to a file.
330 This section documents the functions for managing a history file.
331 int read_history (const char *filename)
333 Add the contents of filename to the history list, a line at a time. If
334 filename is NULL, then read from ~/.history. Returns 0 if successful,
335 or errno if not.
336 int read_history_range (const char *filename, int from, int to)
338 Read a range of lines from filename, adding them to the history list.
339 Start reading at line from and end at to. If from is zero, start at
340 the beginning. If to is less than from, then read until the end of the
341 file. If filename is NULL, then read from ~/.history. Returns 0 if
342 successful, or errno if not.
343 int write_history (const char *filename)
345 Write the current history to filename, overwriting filename if neces‐
346 sary. If filename is NULL, then write the history list to ~/.history.
347 Returns 0 on success, or errno on a read or write error.
348 int append_history (int nelements, const char *filename)
351 Append the last nelements of the history list to filename. If filename
352 is NULL, then append to ~/.history. Returns 0 on success, or errno on
353 a read or write error.
354 int history_truncate_file (const char *filename, int nlines)
356 Truncate the history file filename, leaving only the last nlines lines.
357 If filename is NULL, then ~/.history is truncated. Returns 0 on suc‐
358 cess, or errno on failure.
359 History Expansion
362 These functions implement history expansion.
363 int history_expand (char *string, char **output)
365 Expand string, placing the result into output, a pointer to a string.
366 Returns:
367 0 If no expansions took place (or, if the only change in
368 the text was the removal of escape characters preceding
369 the history expansion character);
370 1 if expansions did take place;
371 -1 if there was an error in expansion;
372 2 if the returned line should be displayed, but not exe‐
373 cuted, as with the :p modifier.
374 If an error ocurred in expansion, then output contains a descriptive
375 error message.
376 char * get_history_event (const char *string, int *cindex, int qchar)
378 Returns the text of the history event beginning at string + *cindex.
379 *cindex is modified to point to after the event specifier. At function
380 entry, cindex points to the index into string where the history event
381 specification begins. qchar is a character that is allowed to end the
382 event specification in addition to the ``normal'' terminating charac‐
383 ters.
384 char ** history_tokenize (const char *string)
386 Return an array of tokens parsed out of string, much as the shell
387 might. The tokens are split on the characters in the his‐
388 tory_word_delimiters variable, and shell quoting conventions are
389 obeyed.
390 char * history_arg_extract (int first, int last, const char *string)
392 Extract a string segment consisting of the first through last arguments
393 present in string. Arguments are split using history_tokenize().
394 History Variables
397 This section describes the externally-visible variables exported by the
398 GNU History Library.
399 int history_base
401 The logical offset of the first entry in the history list.
402 int history_length
404 The number of entries currently stored in the history list.
405 int history_max_entries
407 The maximum number of history entries. This must be changed using sti‐
408 fle_history().
409 int history_wite_timestamps
411 If non-zero, timestamps are written to the history file, so they can be
412 preserved between sessions. The default value is 0, meaning that time‐
413 stamps are not saved. The current timestamp format uses the value of
414 history_comment_char to delimit timestamp entries in the history file.
415 If that variable does not have a value (the default), timestamps will
416 not be written.
417 char history_expansion_char
419 The character that introduces a history event. The default is !. Set‐
420 ting this to 0 inhibits history expansion.
421 char history_subst_char
423 The character that invokes word substitution if found at the start of a
424 line. The default is ^.
425 char history_comment_char
427 During tokenization, if this character is seen as the first character
428 of a word, then it and all subsequent characters up to a newline are
429 ignored, suppressing history expansion for the remainder of the line.
430 This is disabled by default.
431 char * history_word_delimiters
433 The characters that separate tokens for history_tokenize(). The
434 default value is " \t\n()<>;&|".
435 char * history_no_expand_chars
437 The list of characters which inhibit history expansion if found immedi‐
438 ately following history_expansion_char. The default is space, tab,
439 newline, \r, and =.
440 char * history_search_delimiter_chars
442 The list of additional characters which can delimit a history search
443 string, in addition to space, tab, : and ? in the case of a substring
444 search. The default is empty.
445 int history_quotes_inhibit_expansion
447 If non-zero, single-quoted words are not scanned for the history expan‐
448 sion character. The default value is 0.
449 rl_linebuf_func_t * history_inhibit_expansion_function
451 This should be set to the address of a function that takes two argu‐
452 ments: a char * (string) and an int index into that string (i). It
453 should return a non-zero value if the history expansion starting at
454 string[i] should not be performed; zero if the expansion should be
455 done. It is intended for use by applications like bash that use the
456 history expansion character for additional purposes. By default, this
457 variable is set to NULL.
458
460 ~/.history
461 Default filename for reading and writing saved history
462
464 The Gnu Readline Library, Brian Fox and Chet Ramey
465 The Gnu History Library, Brian Fox and Chet Ramey
466 bash(1)
467 readline(3)
468
470 Brian Fox, Free Software Foundation
471 bfox@gnu.org
472 Chet Ramey, Case Western Reserve University
474 chet@ins.CWRU.Edu
475
477 If you find a bug in the history library, you should report it. But
478 first, you should make sure that it really is a bug, and that it
479 appears in the latest version of the history library that you have.
480 Once you have determined that a bug actually exists, mail a bug report
482 to bug-readline@gnu.org. If you have a fix, you are welcome to mail
483 that as well! Suggestions and `philosophical' bug reports may be
484 mailed to bug-readline@gnu.org or posted to the Usenet newsgroup
485 gnu.bash.bug.
486 Comments and bug reports concerning this manual page should be directed
488 to chet@ins.CWRU.Edu.
489GNU History 6.2 2010 August 12 HISTORY(3)