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1994-12-06 03:16:45 +00:00
This is Info file history.info, produced by Makeinfo-1.55 from the
input file hist.texinfo.
This document describes the GNU History library, a programming tool
that provides a consistent user interface for recalling lines of
previously typed input.
Copyright (C) 1988, 1991 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice pare
preserved on all copies.
Permission is granted to copy and distribute modified versions of
this manual under the conditions for verbatim copying, provided that
the entire resulting derived work is distributed under the terms of a
permission notice identical to this one.
Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions, except that this permission notice may be stated in a
translation approved by the Foundation.

File: history.info, Node: Top, Next: Using History Interactively, Prev: (DIR), Up: (DIR)
GNU History Library
*******************
This document describes the GNU History library, a programming tool
that provides a consistent user interface for recalling lines of
previously typed input.
* Menu:
* Using History Interactively:: GNU History User's Manual.
* Programming with GNU History:: GNU History Programmer's Manual.
* Concept Index:: Index of concepts described in this manual.
* Function and Variable Index:: Index of externally visible functions
and variables.

File: history.info, Node: Using History Interactively, Next: Programming with GNU History, Prev: Top, Up: Top
Using History Interactively
***************************
This chapter describes how to use the GNU History Library
interactively, from a user's standpoint. It should be considered a
user's guide. For information on using the GNU History Library in your
own programs, *note Programming with GNU History::..
* Menu:
* History Interaction:: What it feels like using History as a user.

File: history.info, Node: History Interaction, Up: Using History Interactively
History Interaction
===================
The History library provides a history expansion feature that is
similar to the history expansion provided by `csh'. The following text
describes the syntax used to manipulate the history information.
History expansion takes place in two parts. The first is to
determine which line from the previous history should be used during
substitution. The second is to select portions of that line for
inclusion into the current one. The line selected from the previous
history is called the "event", and the portions of that line that are
acted upon are called "words". The line is broken into words in the
same fashion that Bash does, so that several English (or Unix) words
surrounded by quotes are considered as one word.
* Menu:
* Event Designators:: How to specify which history line to use.
* Word Designators:: Specifying which words are of interest.
* Modifiers:: Modifying the results of substitution.

File: history.info, Node: Event Designators, Next: Word Designators, Up: History Interaction
Event Designators
-----------------
An event designator is a reference to a command line entry in the
history list.
`!'
Start a history substitution, except when followed by a space, tab,
the end of the line, = or (.
`!!'
Refer to the previous command. This is a synonym for `!-1'.
`!n'
Refer to command line N.
`!-n'
Refer to the command N lines back.
`!string'
Refer to the most recent command starting with STRING.
`!?string'[`?']
Refer to the most recent command containing STRING.
`!#'
The entire command line typed so far.
`^string1^string2^'
Quick Substitution. Repeat the last command, replacing STRING1
with STRING2. Equivalent to `!!:s/string1/string2/'.

File: history.info, Node: Word Designators, Next: Modifiers, Prev: Event Designators, Up: History Interaction
Word Designators
----------------
A : separates the event specification from the word designator. It
can be omitted if the word designator begins with a ^, $, * or %.
Words are numbered from the beginning of the line, with the first word
being denoted by a 0 (zero).
`0 (zero)'
The `0'th word. For many applications, this is the command word.
`n'
The Nth word.
`^'
The first argument; that is, word 1.
`$'
The last argument.
`%'
The word matched by the most recent `?string?' search.
`x-y'
A range of words; `-Y' abbreviates `0-Y'.
`*'
All of the words, except the `0'th. This is a synonym for `1-$'.
It is not an error to use * if there is just one word in the event;
the empty string is returned in that case.
`x*'
Abbreviates `x-$'
`x-'
Abbreviates `x-$' like `x*', but omits the last word.

File: history.info, Node: Modifiers, Prev: Word Designators, Up: History Interaction
Modifiers
---------
After the optional word designator, you can add a sequence of one or
more of the following modifiers, each preceded by a :.
`h'
Remove a trailing pathname component, leaving only the head.
`r'
Remove a trailing suffix of the form `.'SUFFIX, leaving the
basename.
`e'
Remove all but the trailing suffix.
`t'
Remove all leading pathname components, leaving the tail.
`p'
Print the new command but do not execute it.
`s/old/new/'
Substitute NEW for the first occurrence of OLD in the event line.
Any delimiter may be used in place of /. The delimiter may be
quoted in OLD and NEW with a single backslash. If & appears in
NEW, it is replaced by OLD. A single backslash will quote the &.
The final delimiter is optional if it is the last character on the
input line.
`&'
Repeat the previous substitution.
`g'
Cause changes to be applied over the entire event line. Used in
conjunction with `s', as in `gs/old/new/', or with `&'.

File: history.info, Node: Programming with GNU History, Next: Concept Index, Prev: Using History Interactively, Up: Top
Programming with GNU History
****************************
This chapter describes how to interface programs that you write with
the GNU History Library. It should be considered a technical guide.
For information on the interactive use of GNU History, *note Using
History Interactively::..
* Menu:
* Introduction to History:: What is the GNU History library for?
* History Storage:: How information is stored.
* History Functions:: Functions that you can use.
* History Variables:: Variables that control behaviour.
* History Programming Example:: Example of using the GNU History Library.

File: history.info, Node: Introduction to History, Next: History Storage, Up: Programming with GNU History
Introduction to History
=======================
Many programs read input from the user a line at a time. The GNU
History library is able to keep track of those lines, associate
arbitrary data with each line, and utilize information from previous
lines in composing new ones.
The programmer using the History library has available functions for
remembering lines on a history list, associating arbitrary data with a
line, removing lines from the list, searching through the list for a
line containing an arbitrary text string, and referencing any line in
the list directly. In addition, a history "expansion" function is
available which provides for a consistent user interface across
different programs.
The user using programs written with the History library has the
benefit of a consistent user interface with a set of well-known
commands for manipulating the text of previous lines and using that text
in new commands. The basic history manipulation commands are similar to
the history substitution provided by `csh'.
If the programmer desires, he can use the Readline library, which
includes some history manipulation by default, and has the added
advantage of command line editing.

File: history.info, Node: History Storage, Next: History Functions, Prev: Introduction to History, Up: Programming with GNU History
History Storage
===============
The history list is an array of history entries. A history entry is
declared as follows:
typedef struct _hist_entry {
char *line;
char *data;
} HIST_ENTRY;
The history list itself might therefore be declared as
HIST_ENTRY **the_history_list;
The state of the History library is encapsulated into a single
structure:
/* A structure used to pass the current state of the history stuff around. */
typedef struct _hist_state {
HIST_ENTRY **entries; /* Pointer to the entries themselves. */
int offset; /* The location pointer within this array. */
int length; /* Number of elements within this array. */
int size; /* Number of slots allocated to this array. */
int flags;
} HISTORY_STATE;
If the flags member includes `HS_STIFLED', the history has been
stifled.

File: history.info, Node: History Functions, Next: History Variables, Prev: History Storage, Up: Programming with GNU History
History Functions
=================
This section describes the calling sequence for the various functions
present in GNU History.
* Menu:
* Initializing History and State Management:: Functions to call when you
want to use history in a
program.
* History List Management:: Functions used to manage the list
of history entries.
* Information About the History List:: Functions returning information about
the history list.
* Moving Around the History List:: Functions used to change the position
in the history list.
* Searching the History List:: Functions to search the history list
for entries containing a string.
* Managing the History File:: Functions that read and write a file
containing the history list.
* History Expansion:: Functions to perform csh-like history
expansion.

File: history.info, Node: Initializing History and State Management, Next: History List Management, Up: History Functions
Initializing History and State Management
-----------------------------------------
This section describes functions used to initialize and manage the
state of the History library when you want to use the history functions
in your program.
- Function: void using_history ()
Begin a session in which the history functions might be used. This
initializes the interactive variables.
- Function: HISTORY_STATE * history_get_history_state ()
Return a structure describing the current state of the input
history.
- Function: void history_set_history_state (HISTORY_STATE *state)
Set the state of the history list according to STATE.

File: history.info, Node: History List Management, Next: Information About the History List, Prev: Initializing History and State Management, Up: History Functions
History List Management
-----------------------
These functions manage individual entries on the history list, or set
parameters managing the list itself.
- Function: void add_history (char *string)
Place STRING at the end of the history list. The associated data
field (if any) is set to `NULL'.
- Function: HIST_ENTRY * remove_history (int which)
Remove history entry at offset WHICH from the history. The
removed element is returned so you can free the line, data, and
containing structure.
- Function: HIST_ENTRY * replace_history_entry (int which, char *line,
char *data)
Make the history entry at offset WHICH have LINE and DATA. This
returns the old entry so you can dispose of the data. In the case
of an invalid WHICH, a `NULL' pointer is returned.
- Function: void stifle_history (int max)
Stifle the history list, remembering only the last MAX entries.
- Function: int unstifle_history ()
Stop stifling the history. This returns the previous amount the
history was stifled. The value is positive if the history was
stifled, negative if it wasn't.
- Function: int history_is_stifled ()
Returns non-zero if the history is stifled, zero if it is not.

File: history.info, Node: Information About the History List, Next: Moving Around the History List, Prev: History List Management, Up: History Functions
Information About the History List
----------------------------------
These functions return information about the entire history list or
individual list entries.
- Function: HIST_ENTRY ** history_list ()
Return a `NULL' terminated array of `HIST_ENTRY' which is the
current input history. Element 0 of this list is the beginning of
time. If there is no history, return `NULL'.
- Function: int where_history ()
Returns the offset of the current history element.
- Function: HIST_ENTRY * current_history ()
Return the history entry at the current position, as determined by
`where_history ()'. If there is no entry there, return a `NULL'
pointer.
- Function: HIST_ENTRY * history_get (int offset)
Return the history entry at position OFFSET, starting from
`history_base'. If there is no entry there, or if OFFSET is
greater than the history length, return a `NULL' pointer.
- Function: int history_total_bytes ()
Return the number of bytes that the primary history entries are
using. This function returns the sum of the lengths of all the
lines in the history.

File: history.info, Node: Moving Around the History List, Next: Searching the History List, Prev: Information About the History List, Up: History Functions
Moving Around the History List
------------------------------
These functions allow the current index into the history list to be
set or changed.
- Function: int history_set_pos (int pos)
Set the position in the history list to POS, an absolute index
into the list.
- Function: HIST_ENTRY * previous_history ()
Back up the current history offset to the previous history entry,
and return a pointer to that entry. If there is no previous
entry, return a `NULL' pointer.
- Function: HIST_ENTRY * next_history ()
Move the current history offset forward to the next history entry,
and return the a pointer to that entry. If there is no next
entry, return a `NULL' pointer.

File: history.info, Node: Searching the History List, Next: Managing the History File, Prev: Moving Around the History List, Up: History Functions
Searching the History List
--------------------------
These functions allow searching of the history list for entries
containing a specific string. Searching may be performed both forward
and backward from the current history position. The search may be
"anchored", meaning that the string must match at the beginning of the
history entry.
- Function: int history_search (char *string, int direction)
Search the history for STRING, starting at the current history
offset. If DIRECTION < 0, then the search is through previous
entries, else through subsequent. If STRING is found, then the
current history index is set to that history entry, and the value
returned is the offset in the line of the entry where STRING was
found. Otherwise, nothing is changed, and a -1 is returned.
- Function: int history_search_prefix (char *string, int direction)
Search the history for STRING, starting at the current history
offset. The search is anchored: matching lines must begin with
STRING. If DIRECTION < 0, then the search is through previous
entries, else through subsequent. If STRING is found, then the
current history index is set to that entry, and the return value
is 0. Otherwise, nothing is changed, and a -1 is returned.
- Function: int history_search_pos (char *string, int direction, int
pos)
Search for STRING in the history list, starting at POS, an
absolute index into the list. If DIRECTION is negative, the search
proceeds backward from POS, otherwise forward. Returns the
absolute index of the history element where STRING was found, or
-1 otherwise.

File: history.info, Node: Managing the History File, Next: History Expansion, Prev: Searching the History List, Up: History Functions
Managing the History File
-------------------------
The History library can read the history from and write it to a file.
This section documents the functions for managing a history file.
- Function: int read_history (char *filename)
Add the contents of FILENAME to the history list, a line at a
time. If FILENAME is `NULL', then read from `~/.history'.
Returns 0 if successful, or errno if not.
- Function: int read_history_range (char *filename, int from, int to)
Read a range of lines from FILENAME, adding them to the history
list. Start reading at line FROM and end at TO. If FROM is zero,
start at the beginning. If TO is less than FROM, then read until
the end of the file. If FILENAME is `NULL', then read from
`~/.history'. Returns 0 if successful, or `errno' if not.
- Function: int write_history (char *filename)
Write the current history to FILENAME, overwriting FILENAME if
necessary. If FILENAME is `NULL', then write the history list to
`~/.history'. Values returned are as in `read_history ()'.
- Function: int append_history (int nelements, char *filename)
Append the last NELEMENTS of the history list to FILENAME.
- Function: int history_truncate_file (char *filename, int nlines)
Truncate the history file FILENAME, leaving only the last NLINES
lines.

File: history.info, Node: History Expansion, Prev: Managing the History File, Up: History Functions
History Expansion
-----------------
These functions implement `csh'-like history expansion.
- Function: int history_expand (char *string, char **output)
Expand STRING, placing the result into OUTPUT, a pointer to a
string (*note History Interaction::.). Returns:
`0'
If no expansions took place (or, if the only change in the
text was the de-slashifying of the history expansion
character);
`1'
if expansions did take place;
`-1'
if there was an error in expansion;
`2'
if the returned line should only be displayed, but not
executed, as with the `:p' modifier (*note Modifiers::.).
If an error ocurred in expansion, then OUTPUT contains a
descriptive error message.
- Function: char * history_arg_extract (int first, int last, char
*string)
Extract a string segment consisting of the FIRST through LAST
arguments present in STRING. Arguments are broken up as in Bash.
- Function: char * get_history_event (char *string, int *cindex, int
qchar)
Returns the text of the history event beginning at STRING +
*CINDEX. *CINDEX is modified to point to after the event
specifier. At function entry, CINDEX points to the index into
STRING where the history event specification begins. QCHAR is a
character that is allowed to end the event specification in
addition to the "normal" terminating characters.
- Function: char ** history_tokenize (char *string)
Return an array of tokens parsed out of STRING, much as the shell
might. The tokens are split on white space and on the characters
`()<>;&|$', and shell quoting conventions are obeyed.

File: history.info, Node: History Variables, Next: History Programming Example, Prev: History Functions, Up: Programming with GNU History
History Variables
=================
This section describes the externally visible variables exported by
the GNU History Library.
- Variable: int history_base
The logical offset of the first entry in the history list.
- Variable: int history_length
The number of entries currently stored in the history list.
- Variable: int max_input_history
The maximum number of history entries. This must be changed using
`stifle_history ()'.
- Variable: char history_expansion_char
The character that starts a history event. The default is `!'.
- Variable: char history_subst_char
The character that invokes word substitution if found at the start
of a line. The default is `^'.
- Variable: char history_comment_char
During tokenization, if this character is seen as the first
character of a word, then it and all subsequent characters up to a
newline are ignored, suppressing history expansion for the
remainder of the line. This is disabled by default.
- Variable: char * history_no_expand_chars
The list of characters which inhibit history expansion if found
immediately following HISTORY_EXPANSION_CHAR. The default is
whitespace and `='.

File: history.info, Node: History Programming Example, Prev: History Variables, Up: Programming with GNU History
History Programming Example
===========================
The following program demonstrates simple use of the GNU History
Library.
main ()
{
char line[1024], *t;
int len, done = 0;
line[0] = 0;
using_history ();
while (!done)
{
printf ("history$ ");
fflush (stdout);
t = fgets (line, sizeof (line) - 1, stdin);
if (t && *t)
{
len = strlen (t);
if (t[len - 1] == '\n')
t[len - 1] = '\0';
}
if (!t)
strcpy (line, "quit");
if (line[0])
{
char *expansion;
int result;
result = history_expand (line, &expansion);
if (result)
fprintf (stderr, "%s\n", expansion);
if (result < 0 || result == 2)
{
free (expansion);
continue;
}
add_history (expansion);
strncpy (line, expansion, sizeof (line) - 1);
free (expansion);
}
if (strcmp (line, "quit") == 0)
done = 1;
else if (strcmp (line, "save") == 0)
write_history ("history_file");
else if (strcmp (line, "read") == 0)
read_history ("history_file");
else if (strcmp (line, "list") == 0)
{
register HIST_ENTRY **the_list;
register int i;
the_list = history_list ();
if (the_list)
for (i = 0; the_list[i]; i++)
printf ("%d: %s\n", i + history_base, the_list[i]->line);
}
else if (strncmp (line, "delete", 6) == 0)
{
int which;
if ((sscanf (line + 6, "%d", &which)) == 1)
{
HIST_ENTRY *entry = remove_history (which);
if (!entry)
fprintf (stderr, "No such entry %d\n", which);
else
{
free (entry->line);
free (entry);
}
}
else
{
fprintf (stderr, "non-numeric arg given to `delete'\n");
}
}
}
}

File: history.info, Node: Concept Index, Next: Function and Variable Index, Prev: Programming with GNU History, Up: Top
Concept Index
*************
* Menu:
* anchored search: Searching the History List.
* event designators: Event Designators.
* expansion: History Interaction.
* history events: Event Designators.
* History Searching: Searching the History List.

File: history.info, Node: Function and Variable Index, Prev: Concept Index, Up: Top
Function and Variable Index
***************************
* Menu:
* add_history: History List Management.
* append_history: Managing the History File.
* current_history: Information About the History List.
* get_history_event: History Expansion.
* history_arg_extract: History Expansion.
* history_base: History Variables.
* history_comment_char: History Variables.
* history_expand: History Expansion.
* history_expansion_char: History Variables.
* history_get: Information About the History List.
* history_get_history_state: Initializing History and State Management.
* history_is_stifled: History List Management.
* history_length: History Variables.
* history_list: Information About the History List.
* history_no_expand_chars: History Variables.
* history_search: Searching the History List.
* history_search_pos: Searching the History List.
* history_search_prefix: Searching the History List.
* history_set_history_state: Initializing History and State Management.
* history_set_pos: Moving Around the History List.
* history_subst_char: History Variables.
* history_tokenize: History Expansion.
* history_total_bytes: Information About the History List.
* history_truncate_file: Managing the History File.
* max_input_history: History Variables.
* next_history: Moving Around the History List.
* previous_history: Moving Around the History List.
* read_history: Managing the History File.
* read_history_range: Managing the History File.
* remove_history: History List Management.
* replace_history_entry: History List Management.
* stifle_history: History List Management.
* unstifle_history: History List Management.
* using_history: Initializing History and State Management.
* where_history: Information About the History List.
* write_history: Managing the History File.

Tag Table:
Node: Top975
Node: Using History Interactively1569
Node: History Interaction2077
Node: Event Designators3122
Node: Word Designators3952
Node: Modifiers4936
Node: Programming with GNU History6065
Node: Introduction to History6791
Node: History Storage8112
Node: History Functions9205
Node: Initializing History and State Management10176
Node: History List Management10968
Node: Information About the History List12396
Node: Moving Around the History List13702
Node: Searching the History List14587
Node: Managing the History File16419
Node: History Expansion17925
Node: History Variables19769
Node: History Programming Example21138
Node: Concept Index23742
Node: Function and Variable Index24223

End Tag Table
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