1HISTORY(3)                 Library Functions Manual                 HISTORY(3)
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3
4

NAME

6       history - GNU History Library
7
9       The GNU History Library is Copyright (C) 1989-2002 by the Free Software
10       Foundation, Inc.
11

DESCRIPTION

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

HISTORY EXPANSION

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
23       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
28       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
42   Event Designators
43       An event designator is a reference to a command line entry in the  his‐
44       tory list.
45
46       !      Start  a  history substitution, except when followed by a blank,
47              newline, = or (.
48       !n     Refer to command line n.
49       !-n    Refer to the current command line minus n.
50       !!     Refer to the previous command.  This is a synonym for `!-1'.
51       !string
52              Refer to the most recent command starting with string.
53       !?string[?]
54              Refer to the most recent command containing string.  The  trail‐
55              ing ? may be omitted if string is followed immediately by a new‐
56              line.
57       ^string1^string2^
58              Quick substitution.  Repeat the last command, replacing  string1
59              with string2.  Equivalent to ``!!:s/string1/string2/'' (see Mod‐
60              ifiers below).
61       !#     The entire command line typed so far.
62
63   Word Designators
64       Word designators are used to select desired words from the event.  A  :
65       separates  the event specification from the word designator.  It may be
66       omitted if the word designator begins with a ^, $, *, -, or  %.   Words
67       are  numbered from the beginning of the line, with the first word being
68       denoted by 0 (zero).  Words are inserted into the  current  line  sepa‐
69       rated by single spaces.
70
71       0 (zero)
72              The zeroth word.  For the shell, this is the command word.
73       n      The nth word.
74       ^      The first argument.  That is, word 1.
75       $      The last argument.
76       %      The word matched by the most recent `?string?' search.
77       x-y    A range of words; `-y' abbreviates `0-y'.
78       *      All  of  the words but the zeroth.  This is a synonym for `1-$'.
79              It is not an error to use * if there is just  one  word  in  the
80              event; the empty string is returned in that case.
81       x*     Abbreviates x-$.
82       x-     Abbreviates x-$ like x*, but omits the last word.
83
84       If  a  word  designator is supplied without an event specification, the
85       previous command is used as the event.
86
87   Modifiers
88       After the optional word designator, there may appear a sequence of  one
89       or more of the following modifiers, each preceded by a `:'.
90
91       h      Remove a trailing file name component, leaving only the head.
92       t      Remove all leading file name components, leaving the tail.
93       r      Remove a trailing suffix of the form .xxx, leaving the basename.
94       e      Remove all but the trailing suffix.
95       p      Print the new command but do not execute it.
96       q      Quote the substituted words, escaping further substitutions.
97       x      Quote  the  substituted words as with q, but break into words at
98              blanks and newlines.
99       s/old/new/
100              Substitute new for the first occurrence  of  old  in  the  event
101              line.   Any  delimiter  can  be  used  in place of /.  The final
102              delimiter is optional if it is the last character of  the  event
103              line.   The delimiter may be quoted in old and new with a single
104              backslash.  If & appears in new, it is replaced by old.  A  sin‐
105              gle  backslash  will  quote the &.  If old is null, it is set to
106              the last old substituted, or, if no previous  history  substitu‐
107              tions took place, the last string in a !?string[?]  search.
108       &      Repeat the previous substitution.
109       g      Cause changes to be applied over the entire event line.  This is
110              used in conjunction with `:s' (e.g.,  `:gs/old/new/')  or  `:&'.
111              If  used with `:s', any delimiter can be used in place of /, and
112              the final delimiter is optional if it is the last  character  of
113              the event line.  An a may be used as a synonym for g.
114       G      Apply  the following `s' modifier once to each word in the event
115              line.
116

PROGRAMMING WITH HISTORY FUNCTIONS

118       This section describes how to use the History  library  in  other  pro‐
119       grams.
120
121   Introduction to History
122       The  programmer  using  the History library has available functions for
123       remembering lines on a history list, associating arbitrary data with  a
124       line,  removing  lines  from the list, searching through the list for a
125       line containing an arbitrary text string, and referencing any  line  in
126       the list directly.  In addition, a history expansion function is avail‐
127       able which provides for a consistent user  interface  across  different
128       programs.
129
130       The  user using programs written with the History library has the bene‐
131       fit of a consistent user interface with a set  of  well-known  commands
132       for  manipulating the text of previous lines and using that text in new
133       commands.  The basic history manipulation commands are identical to the
134       history substitution provided by bash.
135
136       If  the  programmer  desires,  he  can  use the Readline library, which
137       includes some history manipulation by default, and has the added advan‐
138       tage of command line editing.
139
140       Before  declaring  any  functions  using  any functionality the History
141       library provides in other code, an application  writer  should  include
142       the  file  <readline/history.h>  in  any  file  that  uses  the History
143       library's features.  It supplies extern declarations  for  all  of  the
144       library's  public functions and variables, and declares all of the pub‐
145       lic data structures.
146
147
148   History Storage
149       The history list is an array of history entries.  A  history  entry  is
150       declared as follows:
151
152       typedef void * histdata_t;
153
154       typedef struct _hist_entry {
155         char *line;
156         char *timestamp;
157         histdata_t data;
158       } HIST_ENTRY;
159
160       The history list itself might therefore be declared as
161
162       HIST_ENTRY ** the_history_list;
163
164       The  state  of the History library is encapsulated into a single struc‐
165       ture:
166
167       /*
168        * A structure used to pass around the current state of the history.
169        */
170       typedef struct _hist_state {
171         HIST_ENTRY **entries; /* Pointer to the entries themselves. */
172         int offset;           /* The location pointer within this array. */
173         int length;           /* Number of elements within this array. */
174         int size;             /* Number of slots allocated to this array. */
175         int flags;
176       } HISTORY_STATE;
177
178       If the flags member includes HS_STIFLED, the history has been stifled.
179

History Functions

181       This section describes the calling sequence for the  various  functions
182       exported by the GNU History library.
183
184   Initializing History and State Management
185       This  section  describes  functions  used  to initialize and manage the
186       state of the History library when you want to use the history functions
187       in your program.
188
189       void using_history (void)
190       Begin  a  session  in  which the history functions might be used.  This
191       initializes the interactive variables.
192
193       HISTORY_STATE * history_get_history_state (void)
194       Return a structure describing the current state of the input history.
195
196       void history_set_history_state (HISTORY_STATE *state)
197       Set the state of the history list according to state.
198
199
200   History List Management
201       These functions manage individual entries on the history list,  or  set
202       parameters managing the list itself.
203
204       void add_history (const char *string)
205       Place string at the end of the history list.  The associated data field
206       (if any) is set to NULL.
207
208       void add_history_time (const char *string)
209       Change the time stamp associated with the most recent history entry  to
210       string.
211
212       HIST_ENTRY * remove_history (int which)
213       Remove  history  entry  at  offset which from the history.  The removed
214       element is returned so you can free  the  line,  data,  and  containing
215       structure.
216
217       histdata_t free_history_entry (HIST_ENTRY *histent)
218       Free  the  history  entry  histent and any history library private data
219       associated with it.  Returns the application-specific data so the call‐
220       er can dispose of it.
221
222       HIST_ENTRY  * replace_history_entry (int which, const char *line, hist‐
223       data_t data)
224       Make the history entry at  offset  which  have  line  and  data.   This
225       returns the old entry so the caller can dispose of any application-spe‐
226       cific data.  In the case  of  an  invalid  which,  a  NULL  pointer  is
227       returned.
228
229       void clear_history (void)
230       Clear the history list by deleting all the entries.
231
232       void stifle_history (int max)
233       Stifle the history list, remembering only the last max entries.
234
235       int unstifle_history (void)
236       Stop  stifling  the  history.   This returns the previously-set maximum
237       number of history entries (as set by  stifle_history()).   history  was
238       stifled.  The value is positive if the history was stifled, negative if
239       it wasn't.
240
241       int history_is_stifled (void)
242       Returns non-zero if the history is stifled, zero if it is not.
243
244
245   Information About the History List
246       These functions return information about the  entire  history  list  or
247       individual list entries.
248
249       HIST_ENTRY ** history_list (void)
250       Return  a  NULL  terminated  array of HIST_ENTRY * which is the current
251       input history.  Element 0 of this list is the beginning  of  time.   If
252       there is no history, return NULL.
253
254       int where_history (void)
255       Returns the offset of the current history element.
256
257       HIST_ENTRY * current_history (void)
258       Return  the  history  entry  at  the current position, as determined by
259       where_history().  If there is no entry there, return a NULL pointer.
260
261       HIST_ENTRY * history_get (int offset)
262       Return the  history  entry  at  position  offset,  starting  from  his‐
263       tory_base.   If  there  is no entry there, or if offset is greater than
264       the history length, return a NULL pointer.
265
266       time_t history_get_time (HIST_ENTRY *)
267       Return the time stamp associated with the history entry passed  as  the
268       argument.
269
270       int history_total_bytes (void)
271       Return  the number of bytes that the primary history entries are using.
272       This function returns the sum of the lengths of all the  lines  in  the
273       history.
274
275
276   Moving Around the History List
277       These functions allow the current index into the history list to be set
278       or changed.
279
280       int history_set_pos (int pos)
281       Set the current history offset to pos, an absolute index into the list.
282       Returns  1  on  success, 0 if pos is less than zero or greater than the
283       number of history entries.
284
285       HIST_ENTRY * previous_history (void)
286       Back up the current history offset to the previous history  entry,  and
287       return  a pointer to that entry.  If there is no previous entry, return
288       a NULL pointer.
289
290       HIST_ENTRY * next_history (void)
291       Move the current history offset forward to the next history entry,  and
292       return  the a pointer to that entry.  If there is no next entry, return
293       a NULL pointer.
294
295
296   Searching the History List
297       These functions allow searching of the history list  for  entries  con‐
298       taining a specific string.  Searching may be performed both forward and
299       backward  from  the  current  history  position.   The  search  may  be
300       anchored,  meaning  that  the string must match at the beginning of the
301       history entry.
302
303       int history_search (const char *string, int direction)
304       Search the history for string, starting at the current history  offset.
305       If  direction  is  less  than  0,  then  the search is through previous
306       entries, otherwise through subsequent entries.   If  string  is  found,
307       then  the  current  history index is set to that history entry, and the
308       value returned is the offset in the line of the entry where string  was
309       found.  Otherwise, nothing is changed, and a -1 is returned.
310
311       int history_search_prefix (const char *string, int direction)
312       Search  the history for string, starting at the current history offset.
313       The search is anchored: matching lines  must  begin  with  string.   If
314       direction  is less than 0, then the search is through previous entries,
315       otherwise through subsequent entries.  If string  is  found,  then  the
316       current  history index is set to that entry, and the return value is 0.
317       Otherwise, nothing is changed, and a -1 is returned.
318
319       int history_search_pos (const char *string, int direction, int pos)
320       Search for string in the history list, starting  at  pos,  an  absolute
321       index  into  the  list.   If direction is negative, the search proceeds
322       backward from pos, otherwise forward.  Returns the  absolute  index  of
323       the history element where string was found, or -1 otherwise.
324
325
326   Managing the History File
327       The  History  library can read the history from and write it to a file.
328       This section documents the functions for managing a history file.
329
330       int read_history (const char *filename)
331       Add the contents of filename to the history list, a line at a time.  If
332       filename  is NULL, then read from ~/.history.  Returns 0 if successful,
333       or errno if not.
334
335       int read_history_range (const char *filename, int from, int to)
336       Read a range of lines from filename, adding them to the  history  list.
337       Start  reading  at  line from and end at to.  If from is zero, start at
338       the beginning.  If to is less than from, then read until the end of the
339       file.   If  filename  is NULL, then read from ~/.history.  Returns 0 if
340       successful, or errno if not.
341
342       int write_history (const char *filename)
343       Write the current history to filename, overwriting filename  if  neces‐
344       sary.   If filename is NULL, then write the history list to ~/.history.
345       Returns 0 on success, or errno on a read or write error.
346
347
348       int append_history (int nelements, const char *filename)
349       Append the last nelements of the history list to filename.  If filename
350       is  NULL, then append to ~/.history.  Returns 0 on success, or errno on
351       a read or write error.
352
353       int history_truncate_file (const char *filename, int nlines)
354       Truncate the history file filename, leaving only the last nlines lines.
355       If  filename  is NULL, then ~/.history is truncated.  Returns 0 on suc‐
356       cess, or errno on failure.
357
358
359   History Expansion
360       These functions implement history expansion.
361
362       int history_expand (char *string, char **output)
363       Expand string, placing the result into output, a pointer to  a  string.
364       Returns:
365              0      If  no  expansions  took place (or, if the only change in
366                     the text was the removal of escape  characters  preceding
367                     the history expansion character);
368              1      if expansions did take place;
369              -1     if there was an error in expansion;
370              2      if  the  returned  line should be displayed, but not exe‐
371                     cuted, as with the :p modifier.
372       If an error ocurred in expansion, then output  contains  a  descriptive
373       error message.
374
375       char * get_history_event (const char *string, int *cindex, int qchar)
376       Returns  the  text  of the history event beginning at string + *cindex.
377       *cindex is modified to point to after the event specifier.  At function
378       entry,  cindex  points to the index into string where the history event
379       specification begins.  qchar is a character that is allowed to end  the
380       event  specification  in addition to the ``normal'' terminating charac‐
381       ters.
382
383       char ** history_tokenize (const char *string)
384       Return an array of tokens parsed out  of  string,  much  as  the  shell
385       might.    The   tokens   are  split  on  the  characters  in  the  his‐
386       tory_word_delimiters  variable,  and  shell  quoting  conventions   are
387       obeyed.
388
389       char * history_arg_extract (int first, int last, const char *string)
390       Extract a string segment consisting of the first through last arguments
391       present in string.  Arguments are split using history_tokenize().
392
393
394   History Variables
395       This section describes the externally-visible variables exported by the
396       GNU History Library.
397
398       int history_base
399       The logical offset of the first entry in the history list.
400
401       int history_length
402       The number of entries currently stored in the history list.
403
404       int history_max_entries
405       The maximum number of history entries.  This must be changed using sti‐
406       fle_history().
407
408       int history_write_timestamps
409       If non-zero, timestamps are written to the history file, so they can be
410       preserved between sessions.  The default value is 0, meaning that time‐
411       stamps are not saved.
412
413       char history_expansion_char
414       The character that introduces a history event.  The default is !.  Set‐
415       ting this to 0 inhibits history expansion.
416
417       char history_subst_char
418       The character that invokes word substitution if found at the start of a
419       line.  The default is ^.
420
421       char history_comment_char
422       During tokenization, if this character is seen as the  first  character
423       of  a  word,  then it and all subsequent characters up to a newline are
424       ignored, suppressing history expansion for the remainder of  the  line.
425       This is disabled by default.
426
427       char * history_word_delimiters
428       The  characters  that  separate  tokens  for  history_tokenize().   The
429       default value is " \t\n()<>;&|".
430
431       char * history_no_expand_chars
432       The list of characters which inhibit history expansion if found immedi‐
433       ately  following  history_expansion_char.   The  default is space, tab,
434       newline, \r, and =.
435
436       char * history_search_delimiter_chars
437       The list of additional characters which can delimit  a  history  search
438       string,  in  addition to space, tab, : and ? in the case of a substring
439       search.  The default is empty.
440
441       int history_quotes_inhibit_expansion
442       If non-zero, single-quoted words are not scanned for the history expan‐
443       sion character.  The default value is 0.
444
445       rl_linebuf_func_t * history_inhibit_expansion_function
446       This  should  be  set to the address of a function that takes two argu‐
447       ments: a char * (string) and an int index into  that  string  (i).   It
448       should  return  a  non-zero  value if the history expansion starting at
449       string[i] should not be performed; zero  if  the  expansion  should  be
450       done.   It  is  intended for use by applications like bash that use the
451       history expansion character for additional purposes.  By default,  this
452       variable is set to NULL.
453

FILES

455       ~/.history
456              Default filename for reading and writing saved history
457

SEE ALSO

459       The Gnu Readline Library, Brian Fox and Chet Ramey
460       The Gnu History Library, Brian Fox and Chet Ramey
461       bash(1)
462       readline(3)
463

AUTHORS

465       Brian Fox, Free Software Foundation
466       bfox@gnu.org
467
468       Chet Ramey, Case Western Reserve University
469       chet@ins.CWRU.Edu
470

BUG REPORTS

472       If  you  find  a bug in the history library, you should report it.  But
473       first, you should make sure that it  really  is  a  bug,  and  that  it
474       appears in the latest version of the history library that you have.
475
476       Once  you have determined that a bug actually exists, mail a bug report
477       to bug-readline@gnu.org.  If you have a fix, you are  welcome  to  mail
478       that  as  well!   Suggestions  and  `philosophical'  bug reports may be
479       mailed to  bug-readline@gnu.org  or  posted  to  the  Usenet  newsgroup
480       gnu.bash.bug.
481
482       Comments and bug reports concerning this manual page should be directed
483       to chet@ins.CWRU.Edu.
484
485
486
487GNU History 6.0                  2003 July 31                       HISTORY(3)
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