Interactive Do

This file documents the Ido package for GNU Emacs.

Copyright © 2013–2022 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with the Front-Cover Texts being “A GNU Manual”, and with the Back-Cover Texts as in (a) below. A copy of the license is included in the section entitled “GNU Free Documentation License”.

(a) The FSF’s Back-Cover Text is: “You have the freedom to copy and modify this GNU manual.”

Table of Contents


1 Overview

This document describes a set of features that can interactively do things with buffers and files. All the features are described here in detail.

The Ido package lets you switch between buffers and visit files and directories with a minimum of keystrokes. It is a superset of Iswitchb, the interactive buffer switching package by Stephen Eglen.

This package was originally written by Kim F. Storm, based on the iswitchb.el package by Stephen Eglen.


1.1 Activation

This package is distributed with Emacs, so there is no need to install any additional files in order to start using it. To activate, use M-x ido-mode.

You may wish to add the following expressions to your initialization file (see The Emacs Initialization File in GNU Emacs Manual), if you make frequent use of features from this package.

(require 'ido)
(ido-mode t)

1.2 Working Directories

Working directories are directories where files have most recently been opened. The current directory is inserted at the front of this ido-work-directory-list whenever a file is opened with ido-find-file and other file-related functions.

User Option: ido-max-work-directory-list

This user option specifies maximum number of working directories to record.

User Option: ido-max-dir-file-cache

This user option specifies maximum number of working directories to be cached. This is the size of the cache of file-name-all-completions results. Each cache entry is time stamped with the modification time of the directory. Some systems, like MS-Windows, have unreliable directory modification times, so you may choose to disable caching on such systems, or explicitly refresh the cache contents using the command ido-reread-directory (usually C-l) in the minibuffer.


2 Matching

This section describes features of this package that have to do with various kinds of matching: among buffers, files, and directories.


2.1 Interactive Substring Matching

As you type in a substring, the list of buffers or files currently matching the substring is displayed as you type. The list is ordered so that the most recent buffers or files visited come at the start of the list.

The buffer or file at the start of the list will be the one visited when you press RET. By typing more of the substring, the list is narrowed down so that gradually the buffer or file you want will be at the top of the list. Alternatively, you can use C-s and C-r (or the right and left arrow keys) to rotate buffer or file names in the list until the one you want is at the top of the list.

Completion is also available so that you can see what is common to all of the matching buffers or files as you type.

For example, if there are two buffers called 123456 and 123, with 123456 the most recent, when using ido-switch-buffer, you first of all get presented with the list of all the buffers

Buffer: {123456 | 123}

If you then press 2:

Buffer: 2[3]{123456 | 123}

The items listed in {...} are the matching buffers, most recent first (buffers visible in the current frame are put at the end of the list by default). At any time you can select the item at the head of the list by pressing RET. You can also put the first element at the end of the list by pressing C-s or RIGHT, or bring the last element to the head of the list by pressing C-r or LEFT.

The item in [...] indicates what can be added to your input by pressing TAB (ido-complete). In this case, you will get "3" added to your input.

So, press TAB:

Buffer: 23{123456 | 123}

At this point, you still have two matching buffers. If you want the first buffer in the list, you can simply press RET. If you want the second in the list, you can press C-s to move it to the top of the list and then press RET to select it.

However, if you type 4, you’ll only have one match left:

Buffer: 234[123456]

Since there is only one matching buffer left, it is given in [] and it is shown in the ido-only-match face (ForestGreen). You can now press TAB or RET to go to that buffer.

If you want to create a new buffer named 234, you can press C-j (ido-select-text) instead of TAB or RET.

If instead, you type a:

Buffer: 234a [No match]

There are no matching buffers. If you press RET or TAB, you can be prompted to create a new buffer called 234a.

Of course, where this function really comes in handy is when you can specify the buffer using only a few keystrokes. In the above example, the quickest way to get to the 123456 file would be just to type 4 and then RET (assuming there isn’t any newer buffer with 4 in its name).

Likewise, if you use C-x C-f (ido-find-file), the list of files and directories in the current directory is provided in the same fashion as the buffers above. The files and directories are normally sorted in alphabetical order, but the most recently visited directory is placed first to speed up navigating to directories that you have visited recently.

In addition to scrolling through the list using <right> and <left>, you can use <up> and <down> to quickly scroll the list to the next or previous subdirectory.

To go down into a subdirectory and continue the file selection on the files in that directory, simply move the directory to the head of the list and hit RET.

To go up to the parent directory, delete any partial file name already specified (e.g., using DEL) and hit DEL.

To go to the root directory (on the current drive), enter two slashes. On MS-DOS or Windows, to select the root of another drive, enter ‘X:/’ where ‘X’ is the drive letter. To go to the home directory, enter ‘~/’. To enter Dired for this directory, use C-d.

You can also visit files on other hosts using the ange-ftp notations ‘/host:’ and ‘/user@host:’.

You can type M-p and M-n to change to previous/next directories from the history, M-s to search for a file matching your input, and M-k to remove the current directory from the history.

If for some reason you cannot specify the proper file using ido-find-file, you can press C-f to enter the normal find-file. You can also press C-b to drop into ido-switch-buffer.


2.2 Prefix Matching

The standard way of completion with *nix shells and Emacs is to insert a prefix and then hitting TAB (or another completion key). Because this behavior has become second nature to a lot of Emacs users, Ido offers, in addition to the default substring matching method (see above), also the prefix matching method. The kind of matching is the only difference to the description of the substring matching above.

You can toggle prefix matching with C-p (ido-toggle-prefix).

For example, if you have two buffers 123456 and 123 then hitting 2 does not match because 2 is not a prefix in any of the buffer names.


2.3 Flexible Matching

User Option: ido-enable-flex-matching

If non-nil, Ido will do flexible string matching. Flexible matching means that if the entered string does not match any item, any item containing the entered characters in the given sequence will match.

If ido-enable-flex-matching is non-nil, Ido will do a more flexible matching (unless regexp matching is active) to find possible matches among the available buffer or file names if no matches are found using the normal prefix or substring matching.

The flexible matching implies that any item which simply contains all of the entered characters in the specified sequence will match.

For example, if you have four files alpha, beta, gamma, and delta, entering ‘aa’ will match alpha and gamma, while ‘ea’ matches beta and delta. If prefix matching is also active, ‘aa’ only matches alpha, while ‘ea’ does not match any files.


2.4 Regular Expression Matching

There is limited provision for regexp matching within Ido, enabled through ido-enable-regexp (toggle with C-t). This allows you to type ‘[ch]$’ for example and see all file names ending in ‘c’ or ‘h’.

User Option: ido-enable-regexp

If the value of this user option is non-nil, Ido will do regexp matching. The value of this user option can be toggled within ido-mode using ido-toggle-regexp.

Please note: Ido-style completion is inhibited when you enable regexp matching.


3 Highlighting

The highlighting of matching items is controlled via ido-use-faces. The faces used are ido-first-match, ido-only-match and ido-subdir.

Coloring of the matching items was suggested by Carsten Dominik.


4 Hidden Buffers and Files

Normally, Ido does not include hidden buffers (whose names start with a space) and hidden files and directories (whose names start with .) in the list of possible completions. However, if the substring you enter does not match any of the visible buffers or files, Ido will automatically look for completions among the hidden buffers or files.

You can toggle the display of hidden buffers and files with C-a (ido-toggle-ignore).


5 Customization

You can customize the ido group to change Ido functionality:

M-x customize-group RET ido RET

or customize a certain variable:

M-x customize-variable RET ido-xxxxx RET

To modify the keybindings, use the ido-setup-hook. For example:

(add-hook 'ido-setup-hook 'ido-my-keys)

(defun ido-my-keys ()
 "Add my keybindings for Ido."
 (define-key ido-completion-map " " 'ido-next-match))

5.1 Changing List Order

By default, the list of current files is most recent first, oldest last, with the exception that the files visible in the current frame are put at the end of the list. A hook exists to allow other functions to order the list. For example, if you add:

(add-hook 'ido-make-buffer-list-hook 'ido-summary-buffers-to-end)

then all files matching "Summary" are moved to the end of the list. (I find this handy for keeping the INBOX Summary and so on out of the way.) It also moves files matching ‘output\*$’ to the end of the list (these are created by AUCTeX when compiling.) Other functions could be made available which alter the list of matching files (either deleting or rearranging elements.)


5.2 Find File At Point

Find File At Point, also known generally as “ffap”, is an intelligent system for opening files and URLs.

The following expression will make Ido guess the context:

(setq ido-use-filename-at-point 'guess)

You can disable URL ffap support by toggling ido-use-url-at-point.

User Option: ido-use-url-at-point

If the value of this user option is non-nil, Ido will look for a URL at point. If found, call find-file-at-point to visit it.


5.3 Ignoring Buffers and Files

Ido is capable of ignoring buffers, directories, files and extensions using regular expressions.

User Option: ido-ignore-buffers

This variable takes a list of regular expressions for buffers to ignore in ido-switch-buffer.

User Option: ido-ignore-directories

This variable takes a list of regular expressions for (sub)directories names to ignore in ido-dired and ido-find-file.

User Option: ido-ignore-files

This variable takes a list of regular expressions for files to ignore in ido-find-file.

User Option: ido-ignore-unc-host-regexps

This variable takes a list of regular expressions matching UNC hosts to ignore. The letter case will be ignored if ido-downcase-unc-hosts is non-nil.

To make Ido use completion-ignored-extensions you need to enable it:

(setq ido-ignore-extensions t)

Now you can customize completion-ignored-extensions as well. Go ahead and add all the useless object files, backup files, shared library files and other computing flotsam you don’t want Ido to show.

Please note: Ido will still complete the ignored elements if it would otherwise not show any other matches. So if you type out the name of an ignored file, Ido will still let you open it just fine.


5.4 Miscellaneous Customization

User Option: ido-mode

This user option determines for which functional group (buffer and files) Ido behavior should be enabled.

User Option: ido-case-fold

If the value of this user option is non-nil, searching of buffer and file names should ignore case.

User Option: ido-show-dot-for-dired

If the value of this user option is non-nil, always put ‘.’ as the first item in file name lists. This allows the current directory to be opened immediately with Dired

User Option: ido-enable-dot-prefix

If the value of this user option is non-nil, Ido will match leading dot as prefix. I.e., hidden files and buffers will match only if you type a dot as first char (even if ido-enable-prefix is nil).

User Option: ido-confirm-unique-completion

If the value of this user option is non-nil, even a unique completion must be confirmed. This means that ido-complete (TAB) must always be followed by ido-exit-minibuffer (RET) even when there is only one unique completion.

User Option: ido-cannot-complete-command

When ido-complete can’t complete any more, it will run the command specified by this user option. The most useful values are ido-completion-help, which pops up a window with completion alternatives, or ido-next-match or ido-prev-match, which cycle the buffer list.

User Option: ido-max-file-prompt-width

This user option specifies the upper limit of the prompt string. If its value is an integer, it specifies the number of characters of the string. If its value is a floating point number, it specifies a fraction of the frame width.

User Option: ido-max-window-height

If the value of this user option is non-nil, its value will override the variable max-mini-window-height, which is the maximum height for resizing mini-windows (the minibuffer and the echo area). If it’s a floating point number, it specifies a fraction of the mini-window frame’s height. If it’s an integer, it specifies the number of lines.

User Option: ido-record-commands

If the value of this user option is non-nil, Ido will record commands in the variable command-history. Note that non-Ido equivalent is recorded.

User Option: ido-all-frames

This user option will be passed to walk-windows as its all-frames argument when Ido is finding buffers. See Cyclic Ordering of Windows in GNU Emacs Lisp Reference Manual.

User Option: ido-minibuffer-setup-hook

This hook variable contains Ido-specific customization of minibuffer setup. It is run during minibuffer setup if Ido is active, and is intended for use in customizing ido for interoperation with other packages.


6 Miscellaneous

After C-x b (ido-switch-buffer), the buffer at the head of the list can be killed by pressing C-k. If the buffer needs saving, you will be queried before the buffer is killed. C-S-b buries the buffer at the end of the list.

Likewise, after C-x C-f, you can delete (i.e., physically remove) the file at the head of the list with C-k. You will always be asked for confirmation before deleting the file.

If you enter C-x b to switch to a buffer visiting a given file, and you find that the file you are after is not in any buffer, you can press C-f to immediately drop into ido-find-file. You can switch back to buffer selection with C-b.

You can also use Ido in your Emacs Lisp programs:

(setq my-pkgs (list "CEDET" "Gnus" "Rcirc" "Tramp" "Org" "all-of-them"))
(ido-completing-read "What's your favorite package? " my-pkgs)

6.1 All Matching

If you have many matching files, they may not all fit onto one line of the minibuffer. Normally, the minibuffer window will grow to show you more of the matching files (depending on the value of the variables resize-mini-windows and max-mini-window-height). If you want Ido to behave differently from the default minibuffer resizing behavior, set the variable ido-max-window-height.

Also, to improve the responsiveness of Ido, the maximum number of matching items is limited to 12, but you can increase or remove this limit via the ido-max-prospects user option.

To see a full list of all matching buffers in a separate buffer, hit ? or press TAB when there are no further completions to the substring. Repeated TAB presses will scroll you through this separate buffer.


6.2 Replacement

ido-read-buffer and ido-read-file-name have been written to be drop-in replacements for the normal buffer and file name reading functions read-buffer and read-file-name.

To use ido for all buffer and file selections in Emacs, customize the variable ido-everywhere.


6.3 Other Packages

If you don’t want to rely on the ido-everywhere functionality, ido-read-buffer, ido-read-file-name, and ido-read-directory-name can be used by other packages to read a buffer name, a file name, or a directory name in the Ido way.


Appendix A GNU Free Documentation License

Version 1.3, 3 November 2008
Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
https://fsf.org/

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
  1. PREAMBLE

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    We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

  2. APPLICABILITY AND DEFINITIONS

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  3. VERBATIM COPYING

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  4. COPYING IN QUANTITY

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  5. MODIFICATIONS

    You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

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    11. For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
    12. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
    13. Delete any section Entitled “Endorsements”. Such a section may not be included in the Modified Version.
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    If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version’s license notice. These titles must be distinct from any other section titles.

    You may add a section Entitled “Endorsements”, provided it contains nothing but endorsements of your Modified Version by various parties—for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

    You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

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  6. COMBINING DOCUMENTS

    You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.

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    In the combination, you must combine any sections Entitled “History” in the various original documents, forming one section Entitled “History”; likewise combine any sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections Entitled “Endorsements.”

  7. COLLECTIONS OF DOCUMENTS

    You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

    You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

  8. AGGREGATION WITH INDEPENDENT WORKS

    A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an “aggregate” if the copyright resulting from the compilation is not used to limit the legal rights of the compilation’s users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

    If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document’s Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.

  9. TRANSLATION

    Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

    If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “History”, the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.

  10. TERMINATION

    You may not copy, modify, sublicense, or distribute the Document except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute it is void, and will automatically terminate your rights under this License.

    However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

    Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

    Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, receipt of a copy of some or all of the same material does not give you any rights to use it.

  11. FUTURE REVISIONS OF THIS LICENSE

    The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See https://www.gnu.org/licenses/.

    Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License “or any later version” applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. If the Document specifies that a proxy can decide which future versions of this License can be used, that proxy’s public statement of acceptance of a version permanently authorizes you to choose that version for the Document.

  12. RELICENSING

    “Massive Multiauthor Collaboration Site” (or “MMC Site”) means any World Wide Web server that publishes copyrightable works and also provides prominent facilities for anybody to edit those works. A public wiki that anybody can edit is an example of such a server. A “Massive Multiauthor Collaboration” (or “MMC”) contained in the site means any set of copyrightable works thus published on the MMC site.

    “CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0 license published by Creative Commons Corporation, a not-for-profit corporation with a principal place of business in San Francisco, California, as well as future copyleft versions of that license published by that same organization.

    “Incorporate” means to publish or republish a Document, in whole or in part, as part of another Document.

    An MMC is “eligible for relicensing” if it is licensed under this License, and if all works that were first published under this License somewhere other than this MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections, and (2) were thus incorporated prior to November 1, 2008.

    The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing.

ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

  Copyright (C)  year  your name.
  Permission is granted to copy, distribute and/or modify this document
  under the terms of the GNU Free Documentation License, Version 1.3
  or any later version published by the Free Software Foundation;
  with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
  Texts.  A copy of the license is included in the section entitled ``GNU
  Free Documentation License''.

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with…Texts.” line with this:

    with the Invariant Sections being list their titles, with
    the Front-Cover Texts being list, and with the Back-Cover Texts
    being list.

If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.


Function Index


Variable Index