1HISTORY(3) Library Functions Manual HISTORY(3)
2
6 history - GNU History Library
7
9 The GNU History Library is Copyright (C) 1989-2017 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. If the maximum number of history entries has
210 been set using stifle_history(), and the new number of history entries
211 would exceed that maximum, the oldest history entry is removed.
212 void add_history_time (const char *string)
214 Change the time stamp associated with the most recent history entry to
215 string.
216 HIST_ENTRY * remove_history (int which)
218 Remove history entry at offset which from the history. The removed
219 element is returned so you can free the line, data, and containing
220 structure.
221 histdata_t free_history_entry (HIST_ENTRY *histent)
223 Free the history entry histent and any history library private data
224 associated with it. Returns the application-specific data so the call‐
225 er can dispose of it.
226 HIST_ENTRY * replace_history_entry (int which, const char *line, hist‐
228 data_t data)
229 Make the history entry at offset which have line and data. This
230 returns the old entry so the caller can dispose of any application-spe‐
231 cific data. In the case of an invalid which, a NULL pointer is
232 returned.
233 void clear_history (void)
235 Clear the history list by deleting all the entries.
236 void stifle_history (int max)
238 Stifle the history list, remembering only the last max entries. The
239 history list will contain only max entries at a time.
240 int unstifle_history (void)
242 Stop stifling the history. This returns the previously-set maximum
243 number of history entries (as set by stifle_history()). history was
244 stifled. The value is positive if the history was stifled, negative if
245 it wasn't.
246 int history_is_stifled (void)
248 Returns non-zero if the history is stifled, zero if it is not.
249 Information About the History List
252 These functions return information about the entire history list or
253 individual list entries.
254 HIST_ENTRY ** history_list (void)
256 Return a NULL terminated array of HIST_ENTRY * which is the current
257 input history. Element 0 of this list is the beginning of time. If
258 there is no history, return NULL.
259 int where_history (void)
261 Returns the offset of the current history element.
262 HIST_ENTRY * current_history (void)
264 Return the history entry at the current position, as determined by
265 where_history(). If there is no entry there, return a NULL pointer.
266 HIST_ENTRY * history_get (int offset)
268 Return the history entry at position offset. The range of valid values
269 of offset starts at history_base and ends at history_length - 1. If
270 there is no entry there, or if offset is outside the valid range,
271 return a NULL pointer.
272 time_t history_get_time (HIST_ENTRY *)
274 Return the time stamp associated with the history entry passed as the
275 argument.
276 int history_total_bytes (void)
278 Return the number of bytes that the primary history entries are using.
279 This function returns the sum of the lengths of all the lines in the
280 history.
281 Moving Around the History List
284 These functions allow the current index into the history list to be set
285 or changed.
286 int history_set_pos (int pos)
288 Set the current history offset to pos, an absolute index into the list.
289 Returns 1 on success, 0 if pos is less than zero or greater than the
290 number of history entries.
291 HIST_ENTRY * previous_history (void)
293 Back up the current history offset to the previous history entry, and
294 return a pointer to that entry. If there is no previous entry, return
295 a NULL pointer.
296 HIST_ENTRY * next_history (void)
298 If the current history offset refers to a valid history entry, incre‐
299 ment the current history offset. If the possibly-incremented history
300 offset refers to a valid history entry, return a pointer to that entry;
301 otherwise, return a NULL pointer.
302 Searching the History List
305 These functions allow searching of the history list for entries con‐
306 taining a specific string. Searching may be performed both forward and
307 backward from the current history position. The search may be
308 anchored, meaning that the string must match at the beginning of the
309 history entry.
310 int history_search (const char *string, int direction)
312 Search the history for string, starting at the current history offset.
313 If direction is less than 0, then the search is through previous
314 entries, otherwise through subsequent entries. If string is found,
315 then the current history index is set to that history entry, and the
316 value returned is the offset in the line of the entry where string was
317 found. Otherwise, nothing is changed, and a -1 is returned.
318 int history_search_prefix (const char *string, int direction)
320 Search the history for string, starting at the current history offset.
321 The search is anchored: matching lines must begin with string. If
322 direction is less than 0, then the search is through previous entries,
323 otherwise through subsequent entries. If string is found, then the
324 current history index is set to that entry, and the return value is 0.
325 Otherwise, nothing is changed, and a -1 is returned.
326 int history_search_pos (const char *string, int direction, int pos)
328 Search for string in the history list, starting at pos, an absolute
329 index into the list. If direction is negative, the search proceeds
330 backward from pos, otherwise forward. Returns the absolute index of
331 the history element where string was found, or -1 otherwise.
332 Managing the History File
335 The History library can read the history from and write it to a file.
336 This section documents the functions for managing a history file.
337 int read_history (const char *filename)
339 Add the contents of filename to the history list, a line at a time. If
340 filename is NULL, then read from ~/.history. Returns 0 if successful,
341 or errno if not.
342 int read_history_range (const char *filename, int from, int to)
344 Read a range of lines from filename, adding them to the history list.
345 Start reading at line from and end at to. If from is zero, start at
346 the beginning. If to is less than from, then read until the end of the
347 file. If filename is NULL, then read from ~/.history. Returns 0 if
348 successful, or errno if not.
349 int write_history (const char *filename)
351 Write the current history to filename, overwriting filename if neces‐
352 sary. If filename is NULL, then write the history list to ~/.history.
353 Returns 0 on success, or errno on a read or write error.
354 int append_history (int nelements, const char *filename)
357 Append the last nelements of the history list to filename. If filename
358 is NULL, then append to ~/.history. Returns 0 on success, or errno on
359 a read or write error.
360 int history_truncate_file (const char *filename, int nlines)
362 Truncate the history file filename, leaving only the last nlines lines.
363 If filename is NULL, then ~/.history is truncated. Returns 0 on suc‐
364 cess, or errno on failure.
365 History Expansion
368 These functions implement history expansion.
369 int history_expand (char *string, char **output)
371 Expand string, placing the result into output, a pointer to a string.
372 Returns:
373 0 If no expansions took place (or, if the only change in
374 the text was the removal of escape characters preceding
375 the history expansion character);
376 1 if expansions did take place;
377 -1 if there was an error in expansion;
378 2 if the returned line should be displayed, but not exe‐
379 cuted, as with the :p modifier.
380 If an error ocurred in expansion, then output contains a descriptive
381 error message.
382 char * get_history_event (const char *string, int *cindex, int qchar)
384 Returns the text of the history event beginning at string + *cindex.
385 *cindex is modified to point to after the event specifier. At function
386 entry, cindex points to the index into string where the history event
387 specification begins. qchar is a character that is allowed to end the
388 event specification in addition to the ``normal'' terminating charac‐
389 ters.
390 char ** history_tokenize (const char *string)
392 Return an array of tokens parsed out of string, much as the shell
393 might. The tokens are split on the characters in the his‐
394 tory_word_delimiters variable, and shell quoting conventions are
395 obeyed.
396 char * history_arg_extract (int first, int last, const char *string)
398 Extract a string segment consisting of the first through last arguments
399 present in string. Arguments are split using history_tokenize().
400 History Variables
403 This section describes the externally-visible variables exported by the
404 GNU History Library.
405 int history_base
407 The logical offset of the first entry in the history list.
408 int history_length
410 The number of entries currently stored in the history list.
411 int history_max_entries
413 The maximum number of history entries. This must be changed using sti‐
414 fle_history().
415 int history_wite_timestamps
417 If non-zero, timestamps are written to the history file, so they can be
418 preserved between sessions. The default value is 0, meaning that time‐
419 stamps are not saved. The current timestamp format uses the value of
420 history_comment_char to delimit timestamp entries in the history file.
421 If that variable does not have a value (the default), timestamps will
422 not be written.
423 char history_expansion_char
425 The character that introduces a history event. The default is !. Set‐
426 ting this to 0 inhibits history expansion.
427 char history_subst_char
429 The character that invokes word substitution if found at the start of a
430 line. The default is ^.
431 char history_comment_char
433 During tokenization, if this character is seen as the first character
434 of a word, then it and all subsequent characters up to a newline are
435 ignored, suppressing history expansion for the remainder of the line.
436 This is disabled by default.
437 char * history_word_delimiters
439 The characters that separate tokens for history_tokenize(). The
440 default value is " \t\n()<>;&|".
441 char * history_no_expand_chars
443 The list of characters which inhibit history expansion if found immedi‐
444 ately following history_expansion_char. The default is space, tab,
445 newline, \r, and =.
446 char * history_search_delimiter_chars
448 The list of additional characters which can delimit a history search
449 string, in addition to space, tab, : and ? in the case of a substring
450 search. The default is empty.
451 int history_quotes_inhibit_expansion
453 If non-zero, double-quoted words are not scanned for the history expan‐
454 sion character or the history comment character. The default value is
455 0.
456 rl_linebuf_func_t * history_inhibit_expansion_function
458 This should be set to the address of a function that takes two argu‐
459 ments: a char * (string) and an int index into that string (i). It
460 should return a non-zero value if the history expansion starting at
461 string[i] should not be performed; zero if the expansion should be
462 done. It is intended for use by applications like bash that use the
463 history expansion character for additional purposes. By default, this
464 variable is set to NULL.
465
467 ~/.history
468 Default filename for reading and writing saved history
469
471 The Gnu Readline Library, Brian Fox and Chet Ramey
472 The Gnu History Library, Brian Fox and Chet Ramey
473 bash(1)
474 readline(3)
475
477 Brian Fox, Free Software Foundation
478 bfox@gnu.org
479 Chet Ramey, Case Western Reserve University
481 chet.ramey@case.edu
482
484 If you find a bug in the history library, you should report it. But
485 first, you should make sure that it really is a bug, and that it
486 appears in the latest version of the history library that you have.
487 Once you have determined that a bug actually exists, mail a bug report
489 to bug-readline@gnu.org. If you have a fix, you are welcome to mail
490 that as well! Suggestions and `philosophical' bug reports may be
491 mailed to bug-readline@gnu.org or posted to the Usenet newsgroup
492 gnu.bash.bug.
493 Comments and bug reports concerning this manual page should be directed
495 to chet.ramey@case.edu.
496GNU History 6.3 2017 October 8 HISTORY(3)