Config File Syntax

The boxes config file is a succession of box design definitions.

Its character encoding is ASCII.

Boxes config files are case insensitive, i.e. upper/lower case does not matter.

Box Design

BOX design_name
END design_name

A box design may optionally have alias names in addition to the primary design name (since boxes v2.1.0). Alias names are appended to the primary design name as a comma-separated list. For example:

BOX design_name, alias1, alias2
END design_name

After the END statement, only the primary design name is specified. There is no practical limit to the number of alias names. Every primary design name and alias name must be unique across the entire config file, including any parent config files.

Every box design definition must have at least a SHAPE block, an ELASTIC list, and a SAMPLE block.


Everything following a pound sign (#) is considered a comment, as long as the pound sign isn’t part of a string or something.

Sample Block


This is the box image used for the list of available designs. The reason why an image is not simply generated is that this way, the box can be shown in an environment in which it might actually be used, e.g. with some C code around (see the boxes config file for many examples).

The sample itself should be indented by 4 spaces. This is because all other samples in the config file are also indented by this value, which simply looks better on the design list.

The ENDS statement must stand on a line of its own, although it may be indented. Such a line cannot occur as part of the sample itself.
The SAMPLE block is a required entry in every box design definition.

Shapes Block

    shape_name (string_list)
    shape_name (string_list)

shape_name may be one of nw, nnw, n, nne, ne, ene, e, ese, se, sse, s, ssw, sw, wsw, w, or wnw, corresponding to the figure shown earlier. The string_list represents the shape itself, line by line. Note that all lines must have equal length. Add extra spaces if necessary. Note also that double quotes (") which appear as part of a string must be escaped by a preceding backslash, so as not to terminate the string early. Consequently, all occurrences of backslashes must also be escaped by adding additional backslashes. The recommended process for creating a string is thus:

  1. Type in the string as you think it should look.
  2. Make your editor double all backslashes within the string.
  3. Escape all double quotes within the string by adding more backslashes.

In Vim, for example, this can be achieved by marking the block, and then typing:


Here are a few examples of valid entries in a SHAPE block:

ne ("+++", "+ +", "+++")
SSE ("///", "\\\\\\")
ene ()
s ("\"")

The delimiter statement can be used to redefine the string delimiting character and the escape character, thus eliminating the above backslash problem. The SHAPE block is a required entry in every box design definition.

Elastic List

ELASTIC (shape_name, shape_name, ...)

Simply lists the shapes which are elastic. Elastic shapes are repeated so that the box can grow and shrink to meet its requested size. Corner shapes may not be elastic. Naturally, there must always be at least one elastic shape per box side. No two neighboring shapes may be elastic. A typical ELASTIC entry would look like this:

elastic (n, e, s, w)

The elastic list is a required entry in every box design definition.

Padding Block

    side_or_group_of_sides value
    side_or_group_of_sides value

Defines the default padding area. Possible values for side_or_group_of_sides are all, horizontal, vertical, top, left, right, or bottom. A padding block may contain an arbitrary number of entries. Entries are read from top to bottom, so that later entries overwrite earlier entries. In the following example:

padding {
    vertical 3
    horiz 2
    left 4

the padding is set to 3 blank lines above the text, 2 spaces to the right of the text, 3 blank lines below the text, and 4 spaces to the left of the text. These values can be overridden by a different specification on the command line using the -p option.

Replace and Reverse Statements

REPLACE "search_pattern" WITH "replacement_string"
REVERSE "search_pattern" TO "replacement_string"

These statements are used to perform substitutions on the text surrounded by a box. The REPLACE statements are executed on the input text when a box is being created. REVERSE statements have the same effect as REPLACE statements, but they are executed after a box has been removed. In the simplest case, one string is replaced with another:

replace "\\*/" with "*-/"
reverse "\\*-/" to "*/"

The REPLACE statement in the above example may be used to quote closing comment tags in the C programming language by inserting a dash between the asterisk and the slash. The REVERSE statement undoes this effect when the box is removed.

The search pattern may be a regular expression, and the replacement string may include backreferences. This gives you quite a powerful means for text modification. The following example is used to insert a space between all characters of the input text:

replace "(.)" with "$1 "
reverse "(.) " to "$1"

There may be many REPLACE/REVERSE statements in one design definition. They will be executed one after the other, starting from the top.

Note that as in all strings, backslashes must be doubled, i.e. boxes “consumes one layer of backslashes”. This is why in the first example, there are two backslashes at the beginning of the search pattern, when only one would have been needed to escape the star operator.

The delimiter statement should not be used to change the string delimiting and escape character in regular expressions. While this is possible, it only affects boxes’ processing, not the regular expression engine’s. This will most likely cause confusion.

You may choose if the replacement is performed once per line or as many times as necessary to replace all occurrences of the sarch pattern (global). Put this indication in front of the search pattern (the default is global):

replace once "foo" with "bar"

We use PCRE2 regular expression syntax. In order to craft the proper regular expressions, online tools such as Regex101 or Regexper might come in handy.

Indentation Mode

INDENT "indentmode"

This sets the default indentation mode for a design. Possible values for indentmode are "box", "text", and "none". The indent mode specifies how existing text indentation is treated.

  • "box", which is the default setting, will cause the box to be indented by the same number of spaces as the text was. The text itself will not be indented within the box, though.
  • "text" will not indent the box, but instead retain the text indentation inside the box.
  • "none" will simply throw away all indentation.

For examples on all three indentation modes please refer to the example page.

String Delimiters


chars must consist of exactly two characters:

  1. the escape character (first character, one of @~?!\)
  2. the string delimiter (second character, one of "~'!|)

No quotes must be placed around those two characters. The effect is that until the end of the current design or until the next DELIMITER statement, all strings must be enclosed not by the usual double quotes ("), but instead by the character you specify. Also, the delimiter may be escaped not by the usual backslash (\), but instead by the escape character you specify. The escape character and the string delimiter must be different characters, of course.
For example, consider the literal string """"", which would normally be written like this:


Using a DELIMITER statement, this looks much simpler:

delimiter \'

This mechanism is intended for box designs which have a lot of backslash or double quote characters in them.

Names of Author and Designer

AUTHOR "name_of_author"

Simply states who the person was who coded the box design definition. This entry is used when displaying the list of designs (boxes -l). The value is free text, but it is good if some contact information is included, for example John Doe <>. These days, such openness with one’s email address may not suit everyone, so feel free to give less or differently formatted author information.

DESIGNER "name_of_designer"

In contrast to author, which tells us who created the config file entry, the designer keyword tells us who created the box design itself. In other words, this is the artist who originally created the ASCII artwork.

Please try to give both fields always. Especially in those cases where existing ASCII art from the internet is adapted for use with boxes, it is important (and good manners) to give credit to the original artist.


Since boxes v2.1.0:

TAGS ("tag1", "tag2", "tag3")

or, in all versions of boxes:

TAGS "tag1, tag2, tag3"

The legacy notation has the advantage of being backwards compatible with all versions of boxes, which is why we use it exclusively in the official config file. But once we’re reasonably sure that all the world is at least on v2.1.0, we can upgrade that.

The tags statement applies one or more tags to the box design which can later be used to find and select the design in a tag query. A tag can only contain the lower-case letters a-z, digits, or a dash (-). It must not start with a dash, and a tag name can be anything but none.

At the end of the output of boxes -l, boxes will print a summary of all tags found in the configuration, complete with counts of how often the tag was encountered.

A tag query can be issued by invoking boxes -q. Boxes will then print the names of all matching box designs. Details about tag queries can be found in the manual page for the -q option.

General Entries

keyword "string_value"

In addition to the author entry, there may be any number of other entries of the above form, giving any kind of information. The boxes config file includes the entries CREATED, REVISION, and REVDATE, to indicate the creation timestamp, revision number, and timestamp of the latest revision, respectively. These other entries are not yet used by boxes, though, and will simply be ignored.

Config File Inheritance

A config file may specify one or more other config files as a “parents” (since boxes v2.1.0). This means that after the config file is read, boxes will also read all the parent configs (in order). If a design is found which we don’t know yet, it is added to the list. In other words, all box designs are “inherited” from the parents, and can be overwritten.

This mechanism works on the box design level. You can only override an entire box design, but not parts of one.

The syntax is

PARENT path_to_parent_config

The path to the parent config should be an absolute pathname specifying a config file (not a directory). Spaces are permitted in this path, and no quotes are used. A parent reference can only occur outside of any box design definitions. The special keyword :global: is used to refer to the boxes global config file.

This syntax implies that there cannot be a comment in the same line as the parent reference - it would be considered part of the file name. Instead, put comments in the line above.

For example, a user wants to add or change a design from the global config. So she creates a config file in ~/.boxes and places a parent :global: statement at the top to inherit the global config. The local / personal config file contains only the changes / additions.

Read on in the next part: A New Box Design Step By Step