2 .\" MAN PAGE COMMENTS to
5 .\" Information Network Services
6 .\" Case Western Reserve University
7 .\" chet.ramey@case.edu
9 .\" Last Change: Sun Oct 8 11:43:43 EDT 2017
11 .TH HISTORY 3 "2017 October 8" "GNU History 6.3"
13 .\" File Name macro. This used to be `.PN', for Path Name,
14 .\" but Sun doesn't seem to like that very much.
21 .\" FnN return-value fun-name N arguments
23 \fI\\$1\fP \fB\\$2\fP \\*(lp\fI\\$3\fP\\*(rp
27 .if t \fI\\$1\fP \fB\\$2\fP \\*(lp\fI\\$3,\|\\$4\fP\\*(rp
28 .if n \fI\\$1\fP \fB\\$2\fP \\*(lp\fI\\$3, \\$4\fP\\*(rp
32 .if t \fI\\$1\fP \fB\\$2\fP \\*(lp\fI\\$3,\|\\$4,\|\\$5\fP\|\\*(rp
33 .if n \fI\\$1\fP \fB\\$2\fP \\*(lp\fI\\$3, \\$4, \\$5\fP\\*(rp
41 history \- GNU History Library
43 .if t The GNU History Library is Copyright \(co 1989-2017 by the Free Software Foundation, Inc.
44 .if n The GNU History Library is Copyright (C) 1989-2017 by the Free Software Foundation, Inc.
46 Many programs read input from the user a line at a time. The 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
51 .SH "HISTORY EXPANSION"
53 The history library supports a history expansion feature that
54 is identical to the history expansion in
56 This section describes what syntax features are available.
58 History expansions introduce words from the history list into
59 the input stream, making it easy to repeat commands, insert the
60 arguments to a previous command into the current input line, or
61 fix errors in previous commands quickly.
63 History expansion is usually performed immediately after a complete line
65 It takes place in two parts.
66 The first is to determine which line from the history list
67 to use during substitution.
68 The second is to select portions of that line for inclusion into
70 The line selected from the history is the \fIevent\fP,
71 and the portions of that line that are acted upon are \fIwords\fP.
72 Various \fImodifiers\fP are available to manipulate the selected words.
73 The line is broken into words in the same fashion as \fBbash\fP
74 does when reading input,
75 so that several words that would otherwise be separated
76 are considered one word when surrounded by quotes (see the
77 description of \fBhistory_tokenize()\fP below).
78 History expansions are introduced by the appearance of the
79 history expansion character, which is \^\fB!\fP\^ by default.
80 Only backslash (\^\fB\e\fP\^) and single quotes can quote
81 the history expansion character.
84 An event designator is a reference to a command line entry in the
86 Unless the reference is absolute, events are relative to the current
87 position in the history list.
92 Start a history substitution, except when followed by a
101 Refer to the current command minus
105 Refer to the previous command. This is a synonym for `!\-1'.
108 Refer to the most recent command
109 preceding the current position in the history list
113 .B !?\fIstring\fR\fB[?]\fR
114 Refer to the most recent command
115 preceding the current position in the history list
118 The trailing \fB?\fP may be omitted if
120 is followed immediately by a newline.
122 .B \d\s+2^\s-2\u\fIstring1\fP\d\s+2^\s-2\u\fIstring2\fP\d\s+2^\s-2\u
123 Quick substitution. Repeat the last command, replacing
128 ``!!:s/\fIstring1\fP/\fIstring2\fP/''
129 (see \fBModifiers\fP below).
132 The entire command line typed so far.
136 Word designators are used to select desired words from the event.
139 separates the event specification from the word designator.
140 It may be omitted if the word designator begins with a
147 Words are numbered from the beginning of the line,
148 with the first word being denoted by 0 (zero).
149 Words are inserted into the current line separated by single spaces.
154 The zeroth word. For the shell, this is the command
161 The first argument. That is, word 1.
164 The last word. This is usually the last argument, but will expand to the
165 zeroth word if there is only one word in the line.
168 The word matched by the most recent `?\fIstring\fR?' search.
171 A range of words; `\-\fIy\fR' abbreviates `0\-\fIy\fR'.
174 All of the words but the zeroth. This is a synonym
175 for `\fI1\-$\fP'. It is not an error to use
178 word in the event; the empty string is returned in that case.
181 Abbreviates \fIx\-$\fP.
184 Abbreviates \fIx\-$\fP like \fBx*\fP, but omits the last word.
187 If a word designator is supplied without an event specification, the
188 previous command is used as the event.
191 After the optional word designator, there may appear a sequence of
192 one or more of the following modifiers, each preceded by a `:'.
198 Remove a trailing file name component, leaving only the head.
201 Remove all leading file name components, leaving the tail.
204 Remove a trailing suffix of the form \fI.xxx\fP, leaving the
208 Remove all but the trailing suffix.
211 Print the new command but do not execute it.
214 Quote the substituted words, escaping further substitutions.
217 Quote the substituted words as with
219 but break into words at
223 .B s/\fIold\fP/\fInew\fP/
226 for the first occurrence of
228 in the event line. Any delimiter can be used in place of /. The
229 final delimiter is optional if it is the last character of the
230 event line. The delimiter may be quoted in
234 with a single backslash. If & appears in
238 A single backslash will quote the &. If
240 is null, it is set to the last
242 substituted, or, if no previous history substitutions took place,
246 .B !?\fIstring\fR\fB[?]\fR
250 Repeat the previous substitution.
253 Cause changes to be applied over the entire event line. This is
254 used in conjunction with `\fB:s\fP' (e.g., `\fB:gs/\fIold\fP/\fInew\fP/\fR')
255 or `\fB:&\fP'. If used with
256 `\fB:s\fP', any delimiter can be used
257 in place of /, and the final delimiter is optional
258 if it is the last character of the event line.
259 An \fBa\fP may be used as a synonym for \fBg\fP.
262 Apply the following `\fBs\fP' modifier once to each word in the event line.
264 .SH "PROGRAMMING WITH HISTORY FUNCTIONS"
265 This section describes how to use the History library in other programs.
266 .SS Introduction to History
268 The programmer using the History library has available functions
269 for remembering lines on a history list, associating arbitrary data
270 with a line, removing lines from the list, searching through the list
271 for a line containing an arbitrary text string, and referencing any line
272 in the list directly. In addition, a history \fIexpansion\fP function
273 is available which provides for a consistent user interface across
276 The user using programs written with the History library has the
277 benefit of a consistent user interface with a set of well-known
278 commands for manipulating the text of previous lines and using that text
279 in new commands. The basic history manipulation commands are
281 the history substitution provided by \fBbash\fP.
283 If the programmer desires, he can use the Readline library, which
284 includes some history manipulation by default, and has the added
285 advantage of command line editing.
287 Before declaring any functions using any functionality the History
288 library provides in other code, an application writer should include
290 .FN <readline/history.h>
291 in any file that uses the
292 History library's features. It supplies extern declarations for all
293 of the library's public functions and variables, and declares all of
294 the public data structures.
298 The history list is an array of history entries. A history entry is
301 .Vb "typedef void *" histdata_t;
304 typedef struct _hist_entry {
311 The history list itself might therefore be declared as
313 .Vb "HIST_ENTRY **" the_history_list;
315 The state of the History library is encapsulated into a single structure:
319 * A structure used to pass around the current state of the history.
321 typedef struct _hist_state {
322 HIST_ENTRY **entries; /* Pointer to the entries themselves. */
323 int offset; /* The location pointer within this array. */
324 int length; /* Number of elements within this array. */
325 int size; /* Number of slots allocated to this array. */
330 If the flags member includes \fBHS_STIFLED\fP, the history has been
332 .SH "History Functions"
334 This section describes the calling sequence for the various functions
335 exported by the GNU History library.
336 .SS Initializing History and State Management
337 This section describes functions used to initialize and manage
338 the state of the History library when you want to use the history
339 functions in your program.
341 .Fn1 void using_history void
342 Begin a session in which the history functions might be used. This
343 initializes the interactive variables.
345 .Fn1 "HISTORY_STATE *" history_get_history_state void
346 Return a structure describing the current state of the input history.
348 .Fn1 void history_set_history_state "HISTORY_STATE *state"
349 Set the state of the history list according to \fIstate\fP.
351 .SS History List Management
353 These functions manage individual entries on the history list, or set
354 parameters managing the list itself.
356 .Fn1 void add_history "const char *string"
357 Place \fIstring\fP at the end of the history list. The associated data
358 field (if any) is set to \fBNULL\fP.
359 If the maximum number of history entries has been set using
360 \fBstifle_history()\fP, and the new number of history entries would exceed
361 that maximum, the oldest history entry is removed.
363 .Fn1 void add_history_time "const char *string"
364 Change the time stamp associated with the most recent history entry to
367 .Fn1 "HIST_ENTRY *" remove_history "int which"
368 Remove history entry at offset \fIwhich\fP from the history. The
369 removed element is returned so you can free the line, data,
370 and containing structure.
372 .Fn1 "histdata_t" free_history_entry "HIST_ENTRY *histent"
373 Free the history entry \fIhistent\fP and any history library private
374 data associated with it. Returns the application-specific data
375 so the caller can dispose of it.
377 .Fn3 "HIST_ENTRY *" replace_history_entry "int which" "const char *line" "histdata_t data"
378 Make the history entry at offset \fIwhich\fP have \fIline\fP and \fIdata\fP.
379 This returns the old entry so the caller can dispose of any
380 application-specific data. In the case
381 of an invalid \fIwhich\fP, a \fBNULL\fP pointer is returned.
383 .Fn1 void clear_history "void"
384 Clear the history list by deleting all the entries.
386 .Fn1 void stifle_history "int max"
387 Stifle the history list, remembering only the last \fImax\fP entries.
388 The history list will contain only \fImax\fP entries at a time.
390 .Fn1 int unstifle_history "void"
391 Stop stifling the history. This returns the previously-set
392 maximum number of history entries (as set by \fBstifle_history()\fP).
393 history was stifled. The value is positive if the history was
394 stifled, negative if it wasn't.
396 .Fn1 int history_is_stifled "void"
397 Returns non-zero if the history is stifled, zero if it is not.
399 .SS Information About the History List
401 These functions return information about the entire history list or
402 individual list entries.
404 .Fn1 "HIST_ENTRY **" history_list "void"
405 Return a \fBNULL\fP terminated array of \fIHIST_ENTRY *\fP which is the
406 current input history. Element 0 of this list is the beginning of time.
407 If there is no history, return \fBNULL\fP.
409 .Fn1 int where_history "void"
410 Returns the offset of the current history element.
412 .Fn1 "HIST_ENTRY *" current_history "void"
413 Return the history entry at the current position, as determined by
414 \fBwhere_history()\fP. If there is no entry there, return a \fBNULL\fP
417 .Fn1 "HIST_ENTRY *" history_get "int offset"
418 Return the history entry at position \fIoffset\fP.
419 The range of valid values of \fIoffset\fP starts at \fBhistory_base\fP
420 and ends at \fBhistory_length\fP \- 1.
421 If there is no entry there, or if \fIoffset\fP is outside the valid
422 range, return a \fBNULL\fP pointer.
424 .Fn1 "time_t" history_get_time "HIST_ENTRY *"
425 Return the time stamp associated with the history entry passed as the argument.
427 .Fn1 int history_total_bytes "void"
428 Return the number of bytes that the primary history entries are using.
429 This function returns the sum of the lengths of all the lines in the
432 .SS Moving Around the History List
434 These functions allow the current index into the history list to be
437 .Fn1 int history_set_pos "int pos"
438 Set the current history offset to \fIpos\fP, an absolute index
440 Returns 1 on success, 0 if \fIpos\fP is less than zero or greater
441 than the number of history entries.
443 .Fn1 "HIST_ENTRY *" previous_history "void"
444 Back up the current history offset to the previous history entry, and
445 return a pointer to that entry. If there is no previous entry, return
446 a \fBNULL\fP pointer.
448 .Fn1 "HIST_ENTRY *" next_history "void"
449 If the current history offset refers to a valid history entry,
450 increment the current history offset.
451 If the possibly-incremented history offset refers to a valid history
452 entry, return a pointer to that entry;
453 otherwise, return a \fBNULL\fP pointer.
455 .SS Searching the History List
457 These functions allow searching of the history list for entries containing
458 a specific string. Searching may be performed both forward and backward
459 from the current history position. The search may be \fIanchored\fP,
460 meaning that the string must match at the beginning of the history entry.
462 .Fn2 int history_search "const char *string" "int direction"
463 Search the history for \fIstring\fP, starting at the current history offset.
464 If \fIdirection\fP is less than 0, then the search is through
465 previous entries, otherwise through subsequent entries.
466 If \fIstring\fP is found, then
467 the current history index is set to that history entry, and the value
468 returned is the offset in the line of the entry where
469 \fIstring\fP was found. Otherwise, nothing is changed, and a -1 is
472 .Fn2 int history_search_prefix "const char *string" "int direction"
473 Search the history for \fIstring\fP, starting at the current history
474 offset. The search is anchored: matching lines must begin with
475 \fIstring\fP. If \fIdirection\fP is less than 0, then the search is
476 through previous entries, otherwise through subsequent entries.
477 If \fIstring\fP is found, then the
478 current history index is set to that entry, and the return value is 0.
479 Otherwise, nothing is changed, and a -1 is returned.
481 .Fn3 int history_search_pos "const char *string" "int direction" "int pos"
482 Search for \fIstring\fP in the history list, starting at \fIpos\fP, an
483 absolute index into the list. If \fIdirection\fP is negative, the search
484 proceeds backward from \fIpos\fP, otherwise forward. Returns the absolute
485 index of the history element where \fIstring\fP was found, or -1 otherwise.
487 .SS Managing the History File
488 The History library can read the history from and write it to a file.
489 This section documents the functions for managing a history file.
491 .Fn1 int read_history "const char *filename"
492 Add the contents of \fIfilename\fP to the history list, a line at a time.
493 If \fIfilename\fP is \fBNULL\fP, then read from \fI~/.history\fP.
494 Returns 0 if successful, or \fBerrno\fP if not.
496 .Fn3 int read_history_range "const char *filename" "int from" "int to"
497 Read a range of lines from \fIfilename\fP, adding them to the history list.
498 Start reading at line \fIfrom\fP and end at \fIto\fP.
499 If \fIfrom\fP is zero, start at the beginning. If \fIto\fP is less than
500 \fIfrom\fP, then read until the end of the file. If \fIfilename\fP is
501 \fBNULL\fP, then read from \fI~/.history\fP. Returns 0 if successful,
502 or \fBerrno\fP if not.
504 .Fn1 int write_history "const char *filename"
505 Write the current history to \fIfilename\fP, overwriting \fIfilename\fP
507 If \fIfilename\fP is \fBNULL\fP, then write the history list to \fI~/.history\fP.
508 Returns 0 on success, or \fBerrno\fP on a read or write error.
511 .Fn2 int append_history "int nelements" "const char *filename"
512 Append the last \fInelements\fP of the history list to \fIfilename\fP.
513 If \fIfilename\fP is \fBNULL\fP, then append to \fI~/.history\fP.
514 Returns 0 on success, or \fBerrno\fP on a read or write error.
516 .Fn2 int history_truncate_file "const char *filename" "int nlines"
517 Truncate the history file \fIfilename\fP, leaving only the last
519 If \fIfilename\fP is \fBNULL\fP, then \fI~/.history\fP is truncated.
520 Returns 0 on success, or \fBerrno\fP on failure.
522 .SS History Expansion
524 These functions implement history expansion.
526 .Fn2 int history_expand "char *string" "char **output"
527 Expand \fIstring\fP, placing the result into \fIoutput\fP, a pointer
528 to a string. Returns:
533 If no expansions took place (or, if the only change in
534 the text was the removal of escape characters preceding the history expansion
538 if expansions did take place;
541 if there was an error in expansion;
544 if the returned line should be displayed, but not executed,
545 as with the \fB:p\fP modifier.
548 If an error ocurred in expansion, then \fIoutput\fP contains a descriptive
551 .Fn3 "char *" get_history_event "const char *string" "int *cindex" "int qchar"
552 Returns the text of the history event beginning at \fIstring\fP +
553 \fI*cindex\fP. \fI*cindex\fP is modified to point to after the event
554 specifier. At function entry, \fIcindex\fP points to the index into
555 \fIstring\fP where the history event specification begins. \fIqchar\fP
556 is a character that is allowed to end the event specification in addition
557 to the ``normal'' terminating characters.
559 .Fn1 "char **" history_tokenize "const char *string"
560 Return an array of tokens parsed out of \fIstring\fP, much as the
562 The tokens are split on the characters in the
563 \fBhistory_word_delimiters\fP variable,
564 and shell quoting conventions are obeyed.
566 .Fn3 "char *" history_arg_extract "int first" "int last" "const char *string"
567 Extract a string segment consisting of the \fIfirst\fP through \fIlast\fP
568 arguments present in \fIstring\fP. Arguments are split using
569 \fBhistory_tokenize()\fP.
571 .SS History Variables
573 This section describes the externally-visible variables exported by
574 the GNU History Library.
577 The logical offset of the first entry in the history list.
579 .Vb int history_length
580 The number of entries currently stored in the history list.
582 .Vb int history_max_entries
583 The maximum number of history entries. This must be changed using
584 \fBstifle_history()\fP.
586 .Vb int history_wite_timestamps
587 If non-zero, timestamps are written to the history file, so they can be
588 preserved between sessions. The default value is 0, meaning that
589 timestamps are not saved.
590 The current timestamp format uses the value of \fIhistory_comment_char\fP
591 to delimit timestamp entries in the history file. If that variable does
592 not have a value (the default), timestamps will not be written.
594 .Vb char history_expansion_char
595 The character that introduces a history event. The default is \fB!\fP.
596 Setting this to 0 inhibits history expansion.
598 .Vb char history_subst_char
599 The character that invokes word substitution if found at the start of
600 a line. The default is \fB^\fP.
602 .Vb char history_comment_char
603 During tokenization, if this character is seen as the first character
604 of a word, then it and all subsequent characters up to a newline are
605 ignored, suppressing history expansion for the remainder of the line.
606 This is disabled by default.
608 .Vb "char *" history_word_delimiters
609 The characters that separate tokens for \fBhistory_tokenize()\fP.
610 The default value is \fB"\ \et\en()<>;&|"\fP.
612 .Vb "char *" history_no_expand_chars
613 The list of characters which inhibit history expansion if found immediately
614 following \fBhistory_expansion_char\fP. The default is space, tab, newline,
615 \fB\er\fP, and \fB=\fP.
617 .Vb "char *" history_search_delimiter_chars
618 The list of additional characters which can delimit a history search
619 string, in addition to space, tab, \fI:\fP and \fI?\fP in the case of
620 a substring search. The default is empty.
622 .Vb int history_quotes_inhibit_expansion
623 If non-zero, double-quoted words are not scanned for the history expansion
624 character or the history comment character. The default value is 0.
626 .Vb "rl_linebuf_func_t *" history_inhibit_expansion_function
627 This should be set to the address of a function that takes two arguments:
628 a \fBchar *\fP (\fIstring\fP)
629 and an \fBint\fP index into that string (\fIi\fP).
630 It should return a non-zero value if the history expansion starting at
631 \fIstring[i]\fP should not be performed; zero if the expansion should
633 It is intended for use by applications like \fBbash\fP that use the history
634 expansion character for additional purposes.
635 By default, this variable is set to \fBNULL\fP.
640 Default filename for reading and writing saved history
645 \fIThe Gnu Readline Library\fP, Brian Fox and Chet Ramey
647 \fIThe Gnu History Library\fP, Brian Fox and Chet Ramey
654 Brian Fox, Free Software Foundation
658 Chet Ramey, Case Western Reserve University
662 If you find a bug in the
664 library, you should report it. But first, you should
665 make sure that it really is a bug, and that it appears in the latest
668 library that you have.
670 Once you have determined that a bug actually exists, mail a
671 bug report to \fIbug\-readline\fP@\fIgnu.org\fP.
672 If you have a fix, you are welcome to mail that
673 as well! Suggestions and `philosophical' bug reports may be mailed
674 to \fPbug-readline\fP@\fIgnu.org\fP or posted to the Usenet
678 Comments and bug reports concerning
679 this manual page should be directed to
680 .IR chet.ramey@case.edu .
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