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# USING MOM

Introduction
Inputting macros
Invoking groff
Previewing documents

## Introduction

As explained in the section What is mom?, mom can be used in two ways: for straight typesetting or for document processing. The difference between the two is that in straight typesetting, every macro is a literal typesetting instruction that determines precisely how text following it will look. Document processing, on the other hand, uses markup "tags" (e.g. `.PP` for paragraphs, `.HEAD` for heads, `.FOOTNOTE` for footnotes, etc.) that make a lot of typesetting decisions automatically.

You tell mom that you want to use the document processing macros with the START macro, explained below. After START, mom determines the appearance of text following the markup tags automatically, although you, the user, can easily change how mom interprets the tags. This gives you nearly complete control over document design. In addition, the typesetting macros, in combination with document processing, let you meet all sorts of typesetting needs that just can't be covered by "one macro fits all" markup tags.

## How to input mom's macros

Regardless of which way you use mom, the following apply.

1. You need a good text editor for inputting mom files.

   I cannot recommend highly enough that you use an editor that lets you write syntax highlighting rules for mom's macros and inline escapes. I use the vi clone called elvis, and find it a pure joy in this regard. Simply colourizing macros and inlines to half-intensity can be enough to make text stand out clearly from formatting commands.

2. All mom's macros begin with a period (dot) and must be entered in upper case (capital) letters.
3. Macro arguments are separated from the macro itself by spaces. Multiple arguments to the same macro are separated from each other by spaces. Any number of spaces may be used. All arguments to a macro must appear on the same line as the macro.
4. Any argument (except a string argument) that is not a digit must be entered in upper case (capital) letters.
5. Any argument that requires a plus or minus sign must have the plus or minus sign prepended to the argument with no intervening space (e.g. +2, -4).
6. Any argument that requires a unit of measure must have the unit appended directly to the argument, with no intervening space (e.g. 4P, .5i, 2v).
7. String arguments, in the sense that the term is used in this manual, must be surrounded by double-quotes ("text of string"). Multiple string arguments are separated from each other by spaces (each argument surrounded by double-quotes, of course).
8. If a string argument, as entered in your text editor, becomes uncomfortably long (i.e. runs longer than the visible portion of your screen or window), you may break it into two or more lines by placing the backslash character (`\`) at the ends of lines to break them up, like this:

       	.SUBTITLE "An In-Depth Consideration of the \
       	Implications of Forty-Two as the Meaning of Life, \
       	The Universe, and Everything"

It's important that formatted documents be easy to read/interpret when you're looking at them in a text editor. One way to achieve this is to group macros that serve a similar purpose together, and separate them from other groups of macros with a blank comment line. In groff, that's done with `\#` on a line by itself. Consider the following, which is a template for starting the chapter of a book.

    	.TITLE   "My Pulitzer Novel"
    	.AUTHOR  "Joe Blow"
    	.CHAPTER  1
    	\#
    	.DOCTYPE    CHAPTER
    	.PRINTSTYLE TYPESET
    	\#
    	.FAM     P
    	.PT_SIZE 10
    	.LS      12
    	\#
    	.START

## Printing -- invoking groff with mom

After you've finished your document, naturally you will want to print it. This involves invoking groff from the command line. In all likelihood, you already know how to do this, but in case you don't, here are two common ways to do it.

    	groff -mom -l <filename>
    	groff -mom <filename> | lpr

In the first, the -l option to groff tells groff to send the output to your printer. In the second, you're doing the same thing, except you're telling groff to pipe the output to your printer. Basically, they're the same thing. The only advantage to the second is that your system may be set up to use something other than lpr as your print command, in which case, you can replace lpr with whatever is appropriate to your box.

Sadly, it is well beyond the scope of this manual to tell you how to set up a printing system. See the README file for minimum requirements to run groff with mom.

NOTE FOR ADVANCED USERS: I've sporadically had groff choke on perfectly innocent sourced files within mom documents. You'll know you have this problem when groff complains that it can't find the sourced file even when you can plainly see that the file exists, and that you've given `.so` the right path and name. Should this happen, pass groff the `-U` (unsafe mode) option along with the other options you require. Theoretically, you only need `-U` with `.open, .opena, .pso, .sy,` and `.pi`, however reality seems, at times, to dictate otherwise.

## How to preview documents

Other than printing out hard copy, there are two well-established methods for previewing your work. Both assume you have a working X server.

Groff itself comes with a quick and dirty previewer called gxditview. Invoke it with

    	groff -X -mom filename

It's not particularly pretty, doesn't have many navigation options, requires a lot of work if you want to use other than the "standard" groff PostScript fonts, and occasionally has difficulty accurately reproducing some of mom's macro effects (smartquotes and leaders come to mind). What it does have going for it is that it's fast and doesn't gobble up system resources.

A surer way to preview documents is with gv (ghostview). This involves processing documents with groff, and directing the output to a PostScript file, like this,

    	groff -mom filename > filename.ps

then opening .ps file in gv.

While that may sound like a lot of work, I've set up my editor (elvis) to do it for me. Whenever I'm working on a document that needs previewing/checking, I fire up gv with the "Watch File" option turned on. To look at the file, I tell elvis to process it (with groff) and send it to a temporary file (`groff -mom filename > filename.ps`), then open the file inside gv. Ever after, when I want to look at any changes I make, I simply tell elvis to work his magic again. The Watch File option in gv registers that the file has changed, and automatically loads the new version. Voilą! --instant previewing.

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