2.4 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 history_max_entries

The maximum number of history entries. This must be changed using stifle_history().

Variable: 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.

Variable: char history_expansion_char

The character that introduces a history event. The default is ‘!’. Setting this to 0 inhibits history expansion.

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_word_delimiters

The characters that separate tokens for history_tokenize(). The default value is " \t\n()<>;&|".

Variable: 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.

Variable: 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, carriage return, and ‘=’.

Variable: int history_quotes_inhibit_expansion

If non-zero, single-quoted words are not scanned for the history expansion character. The default value is 0.

Variable: 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.