This section describes the calling sequence for the various
functions exported by the GNU History library.
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.
void using_history (void)
Begin a session in which the history functions might be used.
This initializes the interactive variables.
HISTORY_STATE * history_get_history_state (void)
Return a structure describing the current state of the input
history.
void history_set_history_state (HISTORY_STATE *state)
Set the state of the history list according to state.
History List Management
These functions manage individual entries on the history list, or
set parameters managing the list itself.
void add_history (const char *string)
Place string at the end of the history list. The associated data
field (if any) is set to NULL. If the maximum number of history
entries has been set using stifle_history(), and the new number
of history entries would exceed that maximum, the oldest history
entry is removed.
void add_history_time (const char *string)
Change the time stamp associated with the most recent history
entry to string.
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.
histdata_t free_history_entry (HIST_ENTRY *histent)
Free the history entry histent and any history library private
data associated with it. Returns the application-specific data
so the caller can dispose of it.
HIST_ENTRY * replace_history_entry (int which, const char *line,
histdata_t data)
Make the history entry at offset which have line and data. This
returns the old entry so the caller can dispose of any
application-specific data. In the case of an invalid which, a
NULL pointer is returned.
void clear_history (void)
Clear the history list by deleting all the entries.
void stifle_history (int max)
Stifle the history list, remembering only the last max entries.
The history list will contain only max entries at a time.
int unstifle_history (void)
Stop stifling the history. This returns the previously-set
maximum number of history entries (as set by stifle_history()).
history was stifled. The value is positive if the history was
stifled, negative if it wasn't.
int history_is_stifled (void)
Returns non-zero if the history is stifled, zero if it is not.
Information About the History List
These functions return information about the entire history list
or individual list entries.
HIST_ENTRY ** history_list (void)
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.
int where_history (void)
Returns the offset of the current history element.
HIST_ENTRY * current_history (void)
Return the history entry at the current position, as determined
by where_history(). If there is no entry there, return a NULL
pointer.
HIST_ENTRY * history_get (int offset)
Return the history entry at position offset. The range of valid
values of offset starts at history_base and ends at
history_length - 1. If there is no entry there, or if offset is
outside the valid range, return a NULL pointer.
time_t history_get_time (HIST_ENTRY *)
Return the time stamp associated with the history entry passed as
the argument.
int history_total_bytes (void)
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.
Moving Around the History List
These functions allow the current index into the history list to
be set or changed.
int history_set_pos (int pos)
Set the current history offset to pos, an absolute index into the
list. Returns 1 on success, 0 if pos is less than zero or
greater than the number of history entries.
HIST_ENTRY * previous_history (void)
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.
HIST_ENTRY * next_history (void)
If the current history offset refers to a valid history entry,
increment the current history offset. If the possibly-
incremented history offset refers to a valid history entry,
return a pointer to that entry; otherwise, return a NULL pointer.
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.
int history_search (const char *string, int direction)
Search the history for string, starting at the current history
offset. If direction is less than 0, then the search is through
previous entries, otherwise through subsequent entries. 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.
int history_search_prefix (const 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 is less than 0, then the search is through
previous entries, otherwise through subsequent entries. 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.
int history_search_pos (const 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.
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.
int read_history (const 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.
int read_history_range (const 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.
int write_history (const char *filename)
Write the current history to filename, overwriting filename if
necessary. If filename is NULL, then write the history list to
~/.history. Returns 0 on success, or errno on a read or write
error.
int append_history (int nelements, const char *filename)
Append the last nelements of the history list to filename. If
filename is NULL, then append to ~/.history. Returns 0 on
success, or errno on a read or write error.
int history_truncate_file (const char *filename, int nlines)
Truncate the history file filename, leaving only the last nlines
lines. If filename is NULL, then ~/.history is truncated.
Returns 0 on success, or errno on failure.
History Expansion
These functions implement history expansion.
int history_expand (char *string, char **output)
Expand string, placing the result into output, a pointer to a
string. Returns:
0 If no expansions took place (or, if the only change
in the text was the removal of escape characters
preceding the history expansion character);
1 if expansions did take place;
-1 if there was an error in expansion;
2 if the returned line should be displayed, but not
executed, as with the :p modifier.
If an error occurred in expansion, then output contains a
descriptive error message.
char * get_history_event (const 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.
char ** history_tokenize (const char *string)
Return an array of tokens parsed out of string, much as the shell
might. The tokens are split on the characters in the
history_word_delimiters variable, and shell quoting conventions
are obeyed.
char * history_arg_extract (int first, int last, const char
*string)
Extract a string segment consisting of the first through last
arguments present in string. Arguments are split using
history_tokenize().
History Variables
This section describes the externally-visible variables exported
by the GNU History Library.
int history_base
The logical offset of the first entry in the history list.
int history_length
The number of entries currently stored in the history list.
int history_max_entries
The maximum number of history entries. This must be changed
using stifle_history().
int history_write_timestamps
If non-zero, timestamps are written to the history file, so they
can be preserved between sessions. The default value is 0,
meaning that timestamps are not saved. The current timestamp
format uses the value of history_comment_char to delimit
timestamp entries in the history file. If that variable does not
have a value (the default), timestamps will not be written.
char history_expansion_char
The character that introduces a history event. The default is !.
Setting this to 0 inhibits history expansion.
char history_subst_char
The character that invokes word substitution if found at the
start of a line. The default is ^.
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.
char * history_word_delimiters
The characters that separate tokens for history_tokenize(). The
default value is " \t\n()<>;&|".
char * history_no_expand_chars
The list of characters which inhibit history expansion if found
immediately following history_expansion_char. The default is
space, tab, newline, \r, and =.
char * history_search_delimiter_chars
The list of additional characters which can delimit a history
search string, in addition to space, tab, : and ? in the case of
a substring search. The default is empty.
int history_quotes_inhibit_expansion
If non-zero, double-quoted words are not scanned for the history
expansion character or the history comment character. The
default value is 0.
rl_linebuf_func_t * history_inhibit_expansion_function
This should be set to the address of a function that takes two
arguments: a char * (string) and an int index into that string
(i). It should return a non-zero value if the history expansion
starting at string[i] should not be performed; zero if the
expansion should be done. It is intended for use by applications
like bash that use the history expansion character for additional
purposes. By default, this variable is set to NULL.
