url.sty ver 1.3 21-JUL-1997 Donald Arseneau asnd@reg.triumf.ca

This package defines "\url", a form of "\verb" that allows linebreaks, and can often be used in the argument to another command. It can be configured to print in different formats, and is particularly useful for hypertext links, email addresses, directories/paths, etc. The font may be selected using the "\urlstyle" command and pre-defined text can be stored with the "\urldef" command. New url-like commands can be defined, and a "\path" command is provided this way.

Usage Conditions:

% \url{ } If the argument contains any "%", "#", or "^^", or ends with "\", it can't be used in the argument to another command.
The argument must not contain unbalanced braces.
% \url| | ...where "|" is any character not used in the argument and not "{" or a space. The same restrictions as above except that the argument may contain unbalanced braces.
% \xyz for "\xyz" a defined-url; this can be used anywhere, no matter what characters it contains.

The "\url" command is fragile, and its argument is likely to be very fragile, but a defined-url is robust.

Package Option: obeyspaces

Ordinarily, all spaces are ignored in the url-text. The "[obeyspaces]" option allows spaces, but may introduce spurious spaces when a url containing "\" characters is given in the argument to another command.
So if you need to obey spaces you can say "\usepackage[obeyspaces]{url}", and if you need both spaces and backslashes, use a `defined-url' for anything with "\".

Package Option: hyphens

Ordinarily, breaks are not allowed after "-" characters because this leads to confusion. (Is the "-" part of the address or just a hyphen?) The package option "[hyphens]" allows breaks after explicit hyphen characters. The "\url" command will *never ever* hyphenate words.

Package Option: spaces

Likewise, breaks are not usually allowed after spaces under the "[obeyspaces]" option, but giving the options "[obeyspaces,spaces]" will allow breaks at those spaces.

Package Option: T1

This signifies that you will be using T1-encoded fonts which contain
some characters missing from most older (OT1) encoded TeX fonts. This
changes the default definition for "\urlstyle{rm}".

Defining a defined-url:

Take for example the email address "myself%node@gateway.net" which could not be given (using "\url" or "\verb") in a caption or parbox due to the percent sign. This address can be predefined with
% \urldef{\myself}\url{myself%node@gateway.net} or
% \urldef{\myself}\url|myself%node@gateway.net|
and then you may use "\myself" instead of "\url{myself%node@gateway.net}"in an argument, and even in a moving argument like a caption because a defined-url is robust.


You can switch the style of printing using "\urlstyle{tt}", where "tt" can be any defined style. The pre-defined styles are "tt", "rm", "sf", and "same" which all allow the same linebreaks but different fonts -- the first three select a specific font and the "same" style uses the current text font. You can define your own styles with different fonts and/or line-breaking by following the explanations below. The "\url" command follows whatever the currently-set style dictates.

Alternate commands:

It may be desireable to have different things treated differently, each in a predefined style; e.g., if you want directory paths to always be in tt and email addresses to be rm, then you would define new url-like commands as follows:

% \newcommand\email{\begingroup \urlstyle{rm}\Url}
% \newcommand\directory{\begingroup \urlstyle{tt}\Url}

You must follow this format closely, and NOTE that the final command is "\Url", not "\url". In fact, the "\directory" example is exactly the "\path" definition which is pre-defined in the package. If you look above, you will see that "\url" is defined with
% \newcommand\url{\begingroup \Url}
I.e., using whatever url-style has been selected.

You can make a defined-url for these other styles, using the usual "\urldef" command as in this example:

% \urldef{\myself}{\email}{myself%node.domain@gateway.net}

which makes "\myself" act like
"% \email{myself%node.domain@gateway.net}",
if the "\email" command is defined as above. The "<\myself" command would then be robust.

Defining styles:

Before describing how to customize the printing style, it is best to mention something about the unusual implementation of "\url". Although the material is textual in nature, and the font specification required is a text-font command, the text is actually typeset in *math* mode.
This allows the context-sensitive linebreaking, but also accounts for the default behavior of ignoring spaces. Now on to defining styles.

To change the font or the list of characters that allow linebreaks, you could redefine the commands "\UrlFont", "\UrlBreaks", "\UrlSpecials" etc. directly in the document, but it is better to define a new 'url-style' (following the example of "\url@ttstyle" and "\url@rmstyle") which defines all of "\UrlBigbreaks", "\UrlNoBreaks", "\UrlBreaks", "\UrlSpecials", and "\UrlFont".

Changing font:

The "\UrlFont" command selects the font. The definition of "\UrlFont" done by the pre-defined styles varies to cope with a variety of LaTeX font selection schemes, but it could be as simple as "\def\UrlFont{\tt}".
Depending on the font selected, some characters may need to be defined in the "\UrlSpecials" list because many fonts don't contain all the standard input characters.

Changing linebreaks:

The list of characters that allow line-breaks is given by "\UrlBreaks" and "\UrlBigBreaks", which have the format "\do\c" for character "c".
The differences are that `BigBreaks' have a lower penalty and have different breakpoints when in sequence (as in "https://"): `BigBreaks' are treated as mathrels while `Breaks' are mathbins (see The TeXbook, p.170). In particular, a series of `BigBreak' characters will break at the end and only at the end; a series of `Break' characters will break % after the first and after every following *pair*; there will be no % break after a `Break' character if a `BigBreak' follows. In the case % of "https://" it doesn't matter whether ":" is a `Break' or `BigBreak' -- the breaks are the same in either case; but for DECnet nodes with "::"
it is important to prevent breaks *between* the colons, and that is why colons are `BigBreaks'.
It is possible for characters to prevent breaks after the next following character (I use this for parentheses). Specify these in "\UrlNoBreaks".

You can do arbitrarily complex things with characters by making them active in math mode (mathcode hex-8000) and specifying the definition(s) in "\UrlSpecials". This is used in the rm and sf styles for OT1 font encoding to handle several characters that are not present in those computer-modern style fonts. See the definition of "\Url@do", which is used by both "\url@rmstyle" and "\url@sfstyle"; it handles missing characters via "\UrlSpecials". The nominal format for setting each special character "c" is: "\do\c{<definition>}", but you can include other definitions too.

If all this sounds confusing ... well, it is! But I hope you won't need to redefine breakpoints -- the default assignments seem to work well for a wide variety of applications. If you do need to make changes, you can test for breakpoints using regular math mode and the characters "+=(a".

Yet more flexibility:
You can also customize the verbatim text by defining "\UrlRight" and/or "\UrlLeft", e.g., for ISO formatting of urls surrounded by "< >", define

% \renewcommand\url{\begingroup \def\UrlLeft{<url: }\def\UrlRight{>}%
% \urlstyle{tt}\Url}

The meanings of "\UrlLeft" and "\UrlRight" are *not* reproduced verbatim.This lets you use formatting commands there, but you must be careful not to use TeX's special characters ("\^_%~#$&{}" etc.) improperly.
You can also define "\UrlLeft" to reprocess the verbatim text, but the format of the definition is special:

% \def\UrlLeft#1\UrlRight{ ... do things with #1 ... }

Yes, that is "#1" followed by "\UrlRight" then the definition. For
example, to put a hyperTeX hypertext link in the DVI file:

% \def\UrlLeft#1\UrlRight{\special{html:<a href="#1">}#1\special{html:</a>}}

Using this technique, url.sty can provide a convenient interface for performing various operations on verbatim text. You don't even need to print out the argument! For greatest efficiency in such obscure applications, you can define a null url-style where all the lists like "\UrlBreaks" are empty.

Revision History:
ver 1.1 6-Feb-1996:
Fix hyphens that wouldn't break and ligatures that weren't suppressed.
ver 1.2 19-Oct-1996:
Package option for T1 encoding; Hooks: "\UrlLeft" and "\UrlRight".
ver 1.3 21-Jul-1997:
Prohibit spaces as delimiter characters; change ascii tilde in OT1.
The End

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