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# Extra readline commands

Extra readline commands

The following extra readline commands are available in Sage:

> - `operate-and-get-next`
> - `history-search-backward-and-save`
> - `history-search-forward-and-save`

The `operate-and-get-next` command accepts the input line and fetches the next line from the history. This is the same command with the same name in the Bash shell.

The `history-search-backward-and-save` command searches backward in the history for the string of characters from the start of the input line to the current cursor position, and fetches the first line found. If the cursor is at the start of the line, the previous line is fetched. The position of the fetched line is saved internally, and the next search begins at the saved position.

The `history-search-forward-and-save` command behaves similarly but forward.

The previous two commands is best used in tandem to fetch a block of lines from the history, by searching backward the first line of the block and then issuing the forward command as many times as needed. They are intended to replace the `history-search-backward` command and the `history-search-forward` command provided by the GNU readline library used in Sage.

To bind these commands with keys, insert the relevant lines into the IPython configuration file `$DOT_SAGE/ipython-*/profile_sage/ipython_config.py`. Note that `$DOT_SAGE` is `$HOME/.sage` by default. For example,

    c = get_config()

    c.InteractiveShell.readline_parse_and_bind = [
        '"\C-o": operate-and-get-next',
        '"\e[A": history-search-backward-and-save',
        '"\e[B": history-search-forward-and-save'
        ]

binds the three commands with the control-o key, the up arrow key, and the down arrow key, respectively. Warning: Sometimes, these keys may be bound to do other actions by the terminal and does not reach to the readline properly (check this by running `stty -a` and reading the `cchars` section). Then you may need to turn off these bindings before the new readline commands work fine . A prominent case is when control-o is bound to `discard` by the terminal. You can turn this off by running `stty discard undef`.

AUTHORS:

> - Kwankyu Lee (2010-11-23): initial version
> - Kwankyu Lee (2013-06-05): updated for the new IPython configuration format.

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