1HISTORY(3) Library Functions Manual HISTORY(3)
2
6 history - GNU History Library
7
9 The GNU History Library is Copyright (C) 1989-2014 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 position
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 word. This is usually the last argument, but will
78 expand to the zeroth word if there is only one word in the line.
79 % The word matched by the most recent `?string?' search.
80 x-y A range of words; `-y' abbreviates `0-y'.
81 * All of the words but the zeroth. This is a synonym for `1-$'.
82 It is not an error to use * if there is just one word in the
83 event; the empty string is returned in that case.
84 x* Abbreviates x-$.
85 x- Abbreviates x-$ like x*, but omits the last word.
86 If a word designator is supplied without an event specification, the
88 previous command is used as the event.
89 Modifiers
91 After the optional word designator, there may appear a sequence of one
92 or more of the following modifiers, each preceded by a `:'.
93 h Remove a trailing file name component, leaving only the head.
95 t Remove all leading file name components, leaving the tail.
96 r Remove a trailing suffix of the form .xxx, leaving the basename.
97 e Remove all but the trailing suffix.
98 p Print the new command but do not execute it.
99 q Quote the substituted words, escaping further substitutions.
100 x Quote the substituted words as with q, but break into words at
101 blanks and newlines.
102 s/old/new/
103 Substitute new for the first occurrence of old in the event
104 line. Any delimiter can be used in place of /. The final
105 delimiter is optional if it is the last character of the event
106 line. The delimiter may be quoted in old and new with a single
107 backslash. If & appears in new, it is replaced by old. A sin‐
108 gle backslash will quote the &. If old is null, it is set to
109 the last old substituted, or, if no previous history substitu‐
110 tions took place, the last string in a !?string[?] search.
111 & Repeat the previous substitution.
112 g Cause changes to be applied over the entire event line. This is
113 used in conjunction with `:s' (e.g., `:gs/old/new/') or `:&'.
114 If used with `:s', any delimiter can be used in place of /, and
115 the final delimiter is optional if it is the last character of
116 the event line. An a may be used as a synonym for g.
117 G Apply the following `s' modifier once to each word in the event
118 line.
119
121 This section describes how to use the History library in other pro‐
122 grams.
123 Introduction to History
125 The programmer using the History library has available functions for
126 remembering lines on a history list, associating arbitrary data with a
127 line, removing lines from the list, searching through the list for a
128 line containing an arbitrary text string, and referencing any line in
129 the list directly. In addition, a history expansion function is avail‐
130 able which provides for a consistent user interface across different
131 programs.
132 The user using programs written with the History library has the bene‐
134 fit of a consistent user interface with a set of well-known commands
135 for manipulating the text of previous lines and using that text in new
136 commands. The basic history manipulation commands are identical to the
137 history substitution provided by bash.
138 If the programmer desires, he can use the Readline library, which
140 includes some history manipulation by default, and has the added advan‐
141 tage of command line editing.
142 Before declaring any functions using any functionality the History
144 library provides in other code, an application writer should include
145 the file <readline/history.h> in any file that uses the History
146 library's features. It supplies extern declarations for all of the
147 library's public functions and variables, and declares all of the pub‐
148 lic data structures.
149 History Storage
152 The history list is an array of history entries. A history entry is
153 declared as follows:
154 typedef void * histdata_t;
156 typedef struct _hist_entry {
158 char *line;
159 char *timestamp;
160 histdata_t data;
161 } HIST_ENTRY;
162 The history list itself might therefore be declared as
164 HIST_ENTRY ** the_history_list;
166 The state of the History library is encapsulated into a single struc‐
168 ture:
169 /*
171 * A structure used to pass around the current state of the history.
172 */
173 typedef struct _hist_state {
174 HIST_ENTRY **entries; /* Pointer to the entries themselves. */
175 int offset; /* The location pointer within this array. */
176 int length; /* Number of elements within this array. */
177 int size; /* Number of slots allocated to this array. */
178 int flags;
179 } HISTORY_STATE;
180 If the flags member includes HS_STIFLED, the history has been stifled.
182
184 This section describes the calling sequence for the various functions
185 exported by the GNU History library.
186 Initializing History and State Management
188 This section describes functions used to initialize and manage the
189 state of the History library when you want to use the history functions
190 in your program.
191 void using_history (void)
193 Begin a session in which the history functions might be used. This
194 initializes the interactive variables.
195 HISTORY_STATE * history_get_history_state (void)
197 Return a structure describing the current state of the input history.
198 void history_set_history_state (HISTORY_STATE *state)
200 Set the state of the history list according to state.
201 History List Management
204 These functions manage individual entries on the history list, or set
205 parameters managing the list itself.
206 void add_history (const char *string)
208 Place string at the end of the history list. The associated data field
209 (if any) is set to NULL.
210 void add_history_time (const char *string)
212 Change the time stamp associated with the most recent history entry to
213 string.
214 HIST_ENTRY * remove_history (int which)
216 Remove history entry at offset which from the history. The removed
217 element is returned so you can free the line, data, and containing
218 structure.
219 histdata_t free_history_entry (HIST_ENTRY *histent)
221 Free the history entry histent and any history library private data
222 associated with it. Returns the application-specific data so the call‐
223 er can dispose of it.
224 HIST_ENTRY * replace_history_entry (int which, const char *line, hist‐
226 data_t data)
227 Make the history entry at offset which have line and data. This
228 returns the old entry so the caller can dispose of any application-spe‐
229 cific data. In the case of an invalid which, a NULL pointer is
230 returned.
231 void clear_history (void)
233 Clear the history list by deleting all the entries.
234 void stifle_history (int max)
236 Stifle the history list, remembering only the last max entries.
237 int unstifle_history (void)
239 Stop stifling the history. This returns the previously-set maximum
240 number of history entries (as set by stifle_history()). history was
241 stifled. The value is positive if the history was stifled, negative if
242 it wasn't.
243 int history_is_stifled (void)
245 Returns non-zero if the history is stifled, zero if it is not.
246 Information About the History List
249 These functions return information about the entire history list or
250 individual list entries.
251 HIST_ENTRY ** history_list (void)
253 Return a NULL terminated array of HIST_ENTRY * which is the current
254 input history. Element 0 of this list is the beginning of time. If
255 there is no history, return NULL.
256 int where_history (void)
258 Returns the offset of the current history element.
259 HIST_ENTRY * current_history (void)
261 Return the history entry at the current position, as determined by
262 where_history(). If there is no entry there, return a NULL pointer.
263 HIST_ENTRY * history_get (int offset)
265 Return the history entry at position offset, starting from his‐
266 tory_base. If there is no entry there, or if offset is greater than
267 the history length, return a NULL pointer.
268 time_t history_get_time (HIST_ENTRY *)
270 Return the time stamp associated with the history entry passed as the
271 argument.
272 int history_total_bytes (void)
274 Return the number of bytes that the primary history entries are using.
275 This function returns the sum of the lengths of all the lines in the
276 history.
277 Moving Around the History List
280 These functions allow the current index into the history list to be set
281 or changed.
282 int history_set_pos (int pos)
284 Set the current history offset to pos, an absolute index into the list.
285 Returns 1 on success, 0 if pos is less than zero or greater than the
286 number of history entries.
287 HIST_ENTRY * previous_history (void)
289 Back up the current history offset to the previous history entry, and
290 return a pointer to that entry. If there is no previous entry, return
291 a NULL pointer.
292 HIST_ENTRY * next_history (void)
294 If the current history offset refers to a valid history entry, incre‐
295 ment the current history offset. If the possibly-incremented history
296 offset refers to a valid history entry, return a pointer to that entry;
297 otherwise, return a NULL pointer.
298 Searching the History List
301 These functions allow searching of the history list for entries con‐
302 taining a specific string. Searching may be performed both forward and
303 backward from the current history position. The search may be
304 anchored, meaning that the string must match at the beginning of the
305 history entry.
306 int history_search (const char *string, int direction)
308 Search the history for string, starting at the current history offset.
309 If direction is less than 0, then the search is through previous
310 entries, otherwise through subsequent entries. If string is found,
311 then the current history index is set to that history entry, and the
312 value returned is the offset in the line of the entry where string was
313 found. Otherwise, nothing is changed, and a -1 is returned.
314 int history_search_prefix (const char *string, int direction)
316 Search the history for string, starting at the current history offset.
317 The search is anchored: matching lines must begin with string. If
318 direction is less than 0, then the search is through previous entries,
319 otherwise through subsequent entries. If string is found, then the
320 current history index is set to that entry, and the return value is 0.
321 Otherwise, nothing is changed, and a -1 is returned.
322 int history_search_pos (const char *string, int direction, int pos)
324 Search for string in the history list, starting at pos, an absolute
325 index into the list. If direction is negative, the search proceeds
326 backward from pos, otherwise forward. Returns the absolute index of
327 the history element where string was found, or -1 otherwise.
328 Managing the History File
331 The History library can read the history from and write it to a file.
332 This section documents the functions for managing a history file.
333 int read_history (const char *filename)
335 Add the contents of filename to the history list, a line at a time. If
336 filename is NULL, then read from ~/.history. Returns 0 if successful,
337 or errno if not.
338 int read_history_range (const char *filename, int from, int to)
340 Read a range of lines from filename, adding them to the history list.
341 Start reading at line from and end at to. If from is zero, start at
342 the beginning. If to is less than from, then read until the end of the
343 file. If filename is NULL, then read from ~/.history. Returns 0 if
344 successful, or errno if not.
345 int write_history (const char *filename)
347 Write the current history to filename, overwriting filename if neces‐
348 sary. If filename is NULL, then write the history list to ~/.history.
349 Returns 0 on success, or errno on a read or write error.
350 int append_history (int nelements, const char *filename)
353 Append the last nelements of the history list to filename. If filename
354 is NULL, then append to ~/.history. Returns 0 on success, or errno on
355 a read or write error.
356 int history_truncate_file (const char *filename, int nlines)
358 Truncate the history file filename, leaving only the last nlines lines.
359 If filename is NULL, then ~/.history is truncated. Returns 0 on suc‐
360 cess, or errno on failure.
361 History Expansion
364 These functions implement history expansion.
365 int history_expand (char *string, char **output)
367 Expand string, placing the result into output, a pointer to a string.
368 Returns:
369 0 If no expansions took place (or, if the only change in
370 the text was the removal of escape characters preceding
371 the history expansion character);
372 1 if expansions did take place;
373 -1 if there was an error in expansion;
374 2 if the returned line should be displayed, but not exe‐
375 cuted, as with the :p modifier.
376 If an error ocurred in expansion, then output contains a descriptive
377 error message.
378 char * get_history_event (const char *string, int *cindex, int qchar)
380 Returns the text of the history event beginning at string + *cindex.
381 *cindex is modified to point to after the event specifier. At function
382 entry, cindex points to the index into string where the history event
383 specification begins. qchar is a character that is allowed to end the
384 event specification in addition to the ``normal'' terminating charac‐
385 ters.
386 char ** history_tokenize (const char *string)
388 Return an array of tokens parsed out of string, much as the shell
389 might. The tokens are split on the characters in the his‐
390 tory_word_delimiters variable, and shell quoting conventions are
391 obeyed.
392 char * history_arg_extract (int first, int last, const char *string)
394 Extract a string segment consisting of the first through last arguments
395 present in string. Arguments are split using history_tokenize().
396 History Variables
399 This section describes the externally-visible variables exported by the
400 GNU History Library.
401 int history_base
403 The logical offset of the first entry in the history list.
404 int history_length
406 The number of entries currently stored in the history list.
407 int history_max_entries
409 The maximum number of history entries. This must be changed using sti‐
410 fle_history().
411 int history_wite_timestamps
413 If non-zero, timestamps are written to the history file, so they can be
414 preserved between sessions. The default value is 0, meaning that time‐
415 stamps are not saved. The current timestamp format uses the value of
416 history_comment_char to delimit timestamp entries in the history file.
417 If that variable does not have a value (the default), timestamps will
418 not be written.
419 char history_expansion_char
421 The character that introduces a history event. The default is !. Set‐
422 ting this to 0 inhibits history expansion.
423 char history_subst_char
425 The character that invokes word substitution if found at the start of a
426 line. The default is ^.
427 char history_comment_char
429 During tokenization, if this character is seen as the first character
430 of a word, then it and all subsequent characters up to a newline are
431 ignored, suppressing history expansion for the remainder of the line.
432 This is disabled by default.
433 char * history_word_delimiters
435 The characters that separate tokens for history_tokenize(). The
436 default value is " \t\n()<>;&|".
437 char * history_no_expand_chars
439 The list of characters which inhibit history expansion if found immedi‐
440 ately following history_expansion_char. The default is space, tab,
441 newline, \r, and =.
442 char * history_search_delimiter_chars
444 The list of additional characters which can delimit a history search
445 string, in addition to space, tab, : and ? in the case of a substring
446 search. The default is empty.
447 int history_quotes_inhibit_expansion
449 If non-zero, double-quoted words are not scanned for the history expan‐
450 sion character or the history comment character. The default value is
451 0.
452 rl_linebuf_func_t * history_inhibit_expansion_function
454 This should be set to the address of a function that takes two argu‐
455 ments: a char * (string) and an int index into that string (i). It
456 should return a non-zero value if the history expansion starting at
457 string[i] should not be performed; zero if the expansion should be
458 done. It is intended for use by applications like bash that use the
459 history expansion character for additional purposes. By default, this
460 variable is set to NULL.
461
463 ~/.history
464 Default filename for reading and writing saved history
465
467 The Gnu Readline Library, Brian Fox and Chet Ramey
468 The Gnu History Library, Brian Fox and Chet Ramey
469 bash(1)
470 readline(3)
471
473 Brian Fox, Free Software Foundation
474 bfox@gnu.org
475 Chet Ramey, Case Western Reserve University
477 chet.ramey@case.edu
478
480 If you find a bug in the history library, you should report it. But
481 first, you should make sure that it really is a bug, and that it
482 appears in the latest version of the history library that you have.
483 Once you have determined that a bug actually exists, mail a bug report
485 to bug-readline@gnu.org. If you have a fix, you are welcome to mail
486 that as well! Suggestions and `philosophical' bug reports may be
487 mailed to bug-readline@gnu.org or posted to the Usenet newsgroup
488 gnu.bash.bug.
489 Comments and bug reports concerning this manual page should be directed
491 to chet.ramey@case.edu.
492GNU History 6.3 2015 May 24 HISTORY(3)